Showing papers on "Lens (optics) published in 1979"

Acoustic microscopy with mechanical scanning—A review

Abstract: Acoustic waves in liquids are known to have wavelengths comparable to that of visible light if the frequency is in the gigahertz range. The phenomena of Brillouin scattering in liquids is based on such waves. In helium near 2 K acoustic waves with a wavelength of 2000 A were studied some ten years ago at UCLA. It follows from these observations that an imaging system based on acoustic radiation with a resolving power competitive with the optical microscope is within reach if an ideal lens free from aberrations could be found. Such a lens, which was so elusive at the beginning, is now a simple device and it is the basic component in the acoustic microscope that forms the basis for this review. In this article we will establish the characteristic properties of this new instrument. We will review some of the simple properties of acoustic waves and show how a single spherical surface formed at a solid liquid interface can serve as this ideal lens free from aberrations and capable of producing diffraction limited beams. When this is incorporated into a mechanical scanning system and excited with acoustic frequencies in the microwave range images can be recorded with acoustic wavelengths equal to the wavelength of visible light. We will present images that show the elastic properties of specimens selected from the fields of material science, integrated circuits, and cell biology. The information content in these images will often exceed that of the optical micrographs. In the reflection mode we illuminate the smooth surface of a crystalline material with a highly convergent acoustic beam. The reflected field is perturbed in a unique way that is determined by the elastic properties of the reflecting surface and it shows up in the phase of the reflected acoustic field. There is a distinct and characteristic response at the output when the spacing between the object and the lens is varied. This behavior in the acoustic ieflection microscope provides a rather simple and direct means for monitoring the elastic parameters of a solid surface. It is easy to distinguish between different materials, to determine the layer thickness, and to display variations in the elastic constants on a microscopic scale. These features lead us to believe there is a promising future for the field of acoustic microscopy.

A high‐intensity scanning ion probe with submicrometer spot size

Abstract: A liquid‐metal gallium‐ion source was imaged by unity‐magnification single‐gap accelerating lens with a postlens deflector to form a focused scanning probe. We report the dependence of the probe diameter and probe current on the lens acceptance half‐angle. The results range between probe diameters of 1000 and 5000 A at currents of 0.12–3.0 nA for half‐angles of 1.2–6 mrad. The current density and brightness at the target for the 1000‐A‐diam 57‐kV probe were 1.5 A/cm2 and 3.3×106 A/cm2 sr, respectively. Astigmatic probes were also produced with dimensions smaller than 1000 A.

Accommodating intraocular implant

Abstract: An eye implant has an optical lens anteriorly convex and posteriorly planar supported on two diametrically opposed coplanar feet through two supporting members forming an arch Each supporting member is unitary with the lens and rooted in one of the feet outside the perimeter of the lens to support the lens with the posterior thereof anterior to the plane of the feet The lens is formed of a rigid biologically inert material The supporting members are formed of soft biologically supporting material The resulting structure, when fixed into the sclera of the eye, will change as to move the lens anteriorly when forces are applied to the feet upon contraction of the ciliary body

Optical switching device

Abstract: Respective end faces of two or more optical waveguides (23 to 29) are connected on one end face of a focussing rod lens (20) and a reflection means (21) having a reflection plane tilted with a specified angle (α) to the normal plane to the lens axis is disposed behind the other end face of the focussing rod lens (20) and angle of reflection plane of the reflection means (21) is varied by rotating the reflection means (21) around the lens axis (203) or by means of a piezo-electric driving device (30), thereby attaining selective switching of the waveguides (from 23 to selected one of 24 or 29) or varying the amount of rays to be transmitted through the waveguides (23 and 24 of FIG. 4), or thereby modulating the rays. By utilizing a semitransparent filter forming another tilted reflection plane, the amount of attenuation for different wavelength or connection of the waveguides are controlled separately.

Welding helmet lens assembly

Abstract: A protective welding lens assembly for use as the eyepiece of a welding helmet in which the lens assembly can be changed from a light-transmitting condition to an essentially opaque condition of very small light transmission, and vice versa, in response to an electrical signal and wherein the electrical signal for changing the light-transmitting characteristics of the lens assembly is controlled by energy emanating from the mouth of the user of the welding helmet. Preferably, the lens assembly comprises a liquid crystal light shutter; however any lens assembly can be used which can be electrically actuated to change its light-transmitting characteristics. A transducer is disposed within the welding helmet so as to be in front of the mouth of the welder when the helmet is positioned over his face. The transducer can comprise either a microphone responsive to sound from the welder's mouth or a pressure transducer responsive to blowing from the welder's mouth. An electrical signal generated by the transducer is then used to control the light-transmitting characteristics of the lens assembly.

Optical system for endoscopes

Abstract: An optical system for endoscopes comprising an objective lens, a plural number of relay lenses for consecutively transferring the image formed with said objective lens and an eyepiece. In said optical system, the whole or portion of one of said relay lenses can be displaced along the optical axis to vary magnification level of said optical system.

Endoscopic method & apparatus including ultrasonic B-scan imaging

Abstract: Endoscopic method and apparatus are provided for the simultaneous visual and ultrasonic imaging of internal body parts through use of a probe insertable into a body cavity. The probe includes a rectilinear transducer array acoustically coupled to the body through a cylindrical focusing lens having an outer face which conforms to the probe contour. The transducer array is included in a pulsed ultrasonic imaging system of the B-scan type. A tube, which includes a flexible portion adjacent the probe, connects the probe to a control housing containing manually operated control mechanism for bending the flexible tube portion. A control handle extends from the side of the housing for control of bending by the operator. The pulsed ultrasonic imaging system includes pulse generator and pulse receiver means connected to individual elements of the transducer array by coaxial cables extending through the tube. Electronic beam focusing and scanning means for rectilinear B-scan operation are provided for imaging of objects at close distances adjacent the probe. Visual display means are provided for visual display of the ultrasonic image from the B-scan receiver. An optical illuminating and viewing system is provided for optically viewing internal body parts through the probe, which system includes an objective lens and illuminating means adjacent the distal ends of the probe and transducer array. A removable eyepiece at the housing is used for direct viewing by the operator while guiding the probe into desired position in the body cavity. Means also are provided for viewing the optical image by a video camera having an output connected to a monitor adjacent the ultrasonic image display. Consequently, both the optical and ultrasonic images are simultaneously displayable and viewable by the operator.

Chirp-grating lens for guided-wave optics

Abstract: A high-throughput diffraction-limited Bragg diffraction grating having a variable periodicity functions as a lens for optical guided waves. The lens may be fabricated with planar photolithograhic techniques. It has predictable focusing properties which are insensitive to process variations making it particularly useful for mass production of integrated optical systems.

Tear flow under hydrogel contact lenses.

Abstract: The tear replenishment rate under three different hydrogel lenses was determined with a slit lamp modified to serve as a fluorophotometer. Fractional tear volume replenishment rates under these lenses averaged 0.011 per blink, which is significantly lower than the 0.10 to 0.20 per blink reported for rigid lenses. These data suggest that the amount of oxygen delivered to the cornea by tear pumping for gel lenses is relatively small and that oxygen received by the cornea covered by a gel lens comes principally by diffusion through the material.

Close-up imaging of documents and displays with lens arrays.

Abstract: An unusually short close-up imaging system about 8.5 cm (3⅜ in.) long has been developed for document copiers, oscilloscope cameras, and computer peripheral hard-copy cameras. Arrays of simple lenses are molded in rows and columns on two parallel plastic lens plates. Each lens on the first lens plate forms a demagnified, inverted, intermediate image of a small area of the object in the space between lens plates. Each lens in the second plate erects and magnifies an intermediate image and places the resulting final image in partially overlapped registration with adjacent images, forming an erect uniform composite image of the whole object.

Mechanical optical switching device

Abstract: The mechanical optical switching device comprises an input optical fiber with a collimating lens (5) and a first and a second output optical fiber each with a converging lens (6 and 7, respectively) at the respective terminal ends. Further there are provided a movable first optical path-changing means (8) and a fixed second and a fixed third optical path-changing means (12 and 13) associated to the first and second output fiber, the three path-changing means (8, 12 and 13) comprising two reflecting surfaces each. For performing the switching operation the first optical path-changing means (8) may be inserted into the optical axis of the collimating input lens (5) or removed therefrom. In the removed position the input beam is directed towards the second output fiber via the third path-changing means (13) and the second output lens (7), and in the inserted position the input beam is directed towards the first output fiber via the first path-changing means (8), second path-changing means (12) and the first output lens (6) Preferably the first path-changing means (8) is a parallelogram prism with the two reflecting surfaces opposite to each other and the second and third path-changing means (12 and 13, respectively) are triangle prisms.

Preferential orientation of contact lenses

Abstract: An improved contact lens and method of forming the same which causes the lens to adopt and maintain a particular angular orientation upon the eye of a wearer. One or more characters are formed in relief upon a surface of the lens at a point which is intended as the topmost point in the lens when properly oriented. The relieved characters may be used alone or in combination with previously-known means for effecting orientation of the lens.

Device for excellently coupling a laser beam to a transmission medium through a lens

Abstract: A device for coupling a laser beam to an end surface of an optical fiber comprises a beam converging lens, a holder for the fiber, a block of a solid material, and a mass of a binder between the block and the end surface and between the block and the holder. The lens and the holder are fixed to each other so as to make the laser beam focus on the end surface. Use is preferred of an arrangement comprising a first and a second holder in which the holders have axial lines, respectively, and hold a laser element for the laser beam and the lens with a beam axis of the laser beam and an optical axis of the lens rendered coincident with the respective axial lines and in which the holders are fixed to each other with the axial lines aligned. The arrangement is effective also in coupling the laser beam to a general transmission medium. Instead of using the arrangement, a lens holder may be fixed to the fiber holder and then to a laser element holder so as to make the laser beam focus on the optical fiber end surface. A nonreflecting coating is desirable on the block at a portion exposed to the incident laser beam either when the laser beam is incident onto the block with a small angle of convergence or when the block is thin. The solid material, the binder, and the optical fiber usually have an approximately equal refractive index.

System for monitoring the movements of one or more point sources of luminous radiation

Abstract: Several virtually punctiform, sequentially excited sources of luminous radiation on a pilot's helmet facilitate continuous determination of the pilot's line of sight with the aid of a linear array of photoelectric cells illuminated via a pair of mutually parallel cylindrical lenses perpendicular to the array. The light path through one of these lenses includes a beam rotator in the form of two juxtaposed prisms which turns one of two sheets of light rays from an excited source, lying originally in two mutually orthogonal planes, through 90° into a plane including the axis of one of the lenses so as to intersect the array in one point while the other sheet of light rays retains its orientation in passing through the axis of the other lens to intersect the array in another point. The locations of the two points of intersection, periodically detected by a charge-coupled scanner, indicate the momentary direction of the active source whose exact position can thus be established with the aid of two radiation sensors of the type described. Alternatively, with three point sources whose mutual distances are known, the positions of these sources can be derived from their respective directions as determined by one such sensor. The nonrotated sheet of rays may pass through a simple prism serving to compensate for the difference in the path lengths of the two sheets. Two pulse counters normally synchronized with the scanner are stepped at half their normal rate in the presence of an output signal from the scanner indicative of incident radiation, thereby determining the position of a cell at or near the middle of a series of neighboring cells illuminated by such radiation.

In-line electron gun

Abstract: The invention provides an in-line electron gun in which first astigmatic lens fields that are convergent in a horizontal direction and divergent in a vertical direction are produced between a first focusing grid and a second focusing grid, and second astigmatic lens fields that are divergent in a horizontal direction and convergent in a vertical direction are produced upstream of the first focusing grid. The lens magnifications in both horizontal and vertical directions can be made substantially equal, so that it is possible to achieve a satisfactory resolution over the entire area of the phosphor screen and also to prevent moire occurrences.

An asymmetric electrostatic lens for field‐emission microprobe applications

Abstract: The properties of a physically asymmetric three‐element electrostatic lens have been calculated numerically for voltage‐symmetric and voltage‐asymmetric cases. The lens has low chromatic aberration, Cc∞/f < 0.5, when operated in the voltage‐asymmetric mode with voltage ratios Vfinal/Vinitial as low as 2. Calculations of beam diameter versus current with realistic field electron emission parameters of dI/dΩ=1 mA sr−1 and ΔE=2 eV at 5 kV emitter voltage show that at 30‐kV final‐beam voltage 250 nA current could be focused into a 0.25‐μm spot at 5 cm working distance, with an emitter‐lens separation of 1.5 cm. It is shown that while the two‐element immersion lens is inappropriate for high‐current microprobe applications, the three‐element asymmetric lens is well suited for this work.

Light Scattering and Reversible Cataracts in the Calf and Human Lens

Abstract: By using measurements of the intensity of light scattered from intact calf lenses, we have determined a number of reagents that induce nuclear and cortical opacification at body temperature. Diffusion of buffered saline solutions of glycerol, other glycols, urea, guanidine hydrochloride or glycine into the lens reverses the opacity of all the reagent-induced cataracts. Similar findings are obtained with lens homogenates, which have gel-like properties as determined from viscosity measurements. A 50 % (by volume) glycerol or 5 M urea solution clarifies human pathologic cataractous lenses by reducing the opacification due to light scattering. These findings suggest that it may be possible, in principle, to reverse human lens cataracts chemically in situ . The scattering of laser light from quasi-periodic lattice of normal lens cells produces a regular diffraction pattern containing many Bragg spots whose positions are those predicted from the basis vectors of the cellular lattice. The intensity of the Bragg reflexions increases greatly when cataracts are formed in the calf and human lens, and falls greatly when the lenses are clarified. The spatial variation in the scattered light intensity of the Bragg spots and between these spots contains detailed information on the structure of the scattering elements associated with opacification.

Contrast and imaging performance in the scanning acoustic microscope

Abstract: Several articles have been written on the subject of scanning acoustic microscopy. Nevertheless, apart from some specific papers dealing with reflection microscopy, little has been said about the various contrast mechanisms involved in the process of image formation, and the effects of parameters such as acoustic antireflection coatings on the lens surface and absorption in the water on the quality of the recorded image. This paper is devoted to an analysis of these problems. It is shown that in the amplitude mode of operation, the acoustic microscope acts as a phase contrast microscope and is sensitive to the local phase gradients in the object. Furthermore, it is shown that the effect of an acoustic antireflection coating on the lens surface is to substantially reduce the side lobe amplitude of the focal distribution at the expense of a slight increase in the width of the main lobe. Experimental observations agree with theory.

Compact optical structure with integrated source

Abstract: The invention relates to a compact optical structure comprising a semiconductor emitter junction, a laser or a light emitting diode, coupled to a plane waveguide formed by a layer of photo-polymer deposited on a substrate with a suitable index. A surface layer, of photo-polymer for example, enables the registration of photo-induced diffraction structures performing particular optical functions such as that of a distributed reflector, deflector or lens. Such compact structures are applicable, in particular to the designing of simple, small devices, laser sources with distributed external resonators, interferometric gyrometers, hydrophones, multiplexers or demultiplexers.

Defect detection system

Abstract: A laser beam projected through a prism in a direction normal to the surface of a circular wafer is focused into a spot area and scanned along a spiral path on this surface. The focusing means comprises a relatively large aperture lens and the prism is on the lens axis. The retroreflected specular light passes through the lens and is prevented from reaching a light detector in the image plane of the lens by the prism. When the beam illuminates a microscopic surface defect on the wafer, the light is diffracted and reflected therefrom, and the lens captures that portion of the reflected light within the solid angle subtended by the lens, and passes that portion thereof not blocked by the prism, to the light detector. The output of the detector may be employed to intensity modulate the beam of a cathode-ray tube display, the beam of which is spirally scanned in synchronism with the scanning of the light beam.

Optical fibre connectors

Abstract: An optical fibre connector comprising in respect of each of the optical fibres to be connected, a connector body part formed at one end with a recess which accurately locates a sphere lens relative to an optical fibre receiving hole extending through the body part and terminating at the center of the recess whereby the axis of the optical fibre received by the hole and preferably bonded to the surface of the sphere lens. Connecting means is provided for connecting together in axial alignment two of the body parts with the sphere lenses of the parts arranged in opposed relationship.

Three dimensional television system

Abstract: A method and apparatus for producing a three-dimensional picture suitable for use with television systems. A set of representations of differing cross-sections of a scene is displayed on one or more display screens (19, 20, 21, 22). These displayed representations are optically stacked along a common optical axis by an arrangement of beam splitters (26) to form a composite three-dimensional picture. At least one positive lens (92) is included within the apparatus for repositioning the composite picture forward toward a viewing audience. A method and apparatus are also disclosed for enlarging the picture (80, 81), minimizing translucency therein and developing multiple viewing locations (100, 101) for increasing audience enjoyment.

Highly concentrating Fresnel lenses.

Abstract: A new type of convex Fresnel lens is discussed capable of concentrating solar radiation very near the ultimate concentration limit. The differential equations that describe the lens are solved to provide computed solutions, which are then checked by ray tracing techniques. The performance (efficiency and concentration) of the lens is investigated and compared with that of a flat Fresnel lens, showing that the new lens is preferable for concentrating solar radiation.

Design techniques for forming 488-nm holographic lenses with reconstruction at 633 nm

Abstract: A new design technique is presented for designing holographic lenses based on a K-vector closure principle. The technique enables closed and open loop ray tracing for design optimization and image analysis. A set of APL computer programs has been written for implementation. They are described in detail along with experimental results from holograms constructed at 488 nm and read out at 633 nm.

Effects of lens aberrations in some experiments of speckle interferometry

Abstract: For studying the effects of lens aberrations, the authors have calculated the change in the complex amplitude in the pupil of the optical system between the two exposures. The complex amplitude in the pupil may be considered as the product of a 'speckle' function-produced from the diffusing object-and a 'pupil' function, where the lens aberrations are represented by a phase term. The authors show that the translation of speckle pattern relative to the pupil gives rise to an additional phase term in the second exposure which is a function of lens aberrations. This phase term enables one to evaluate the deformation or loss of visibility on the speckle interference fringes in the Fourier plane. In the case where the translation is uniform the effects are completely shown. The effects of lens aberrations in other classical experiments are briefly discussed.