Showing papers on "Lens (optics) published in 1972"

Displacement Measurement from Double-exposure Laser Photographs

Abstract: Surface displacement can be measured by recording a double-exposure photograph of the laser-illuminated object, followed by optical processing of the recorded speckle-pattern image. The analysis can either be on a point-by-point basis, or by a spatial filtering technique which resolves the motion in any desired direction orthogonal to the line of sight. The limits within which the technique may be used to measure lateral translations and rotations of the surface are examined theoretically and experimentally, and the effect of lens aberrations and surface scattering properties are discussed. Surface tilt may also be measured by recording a defocused double exposure image and analysing its optical transform. The photographic techniques described can be extended to measuring surface vibration, by recording a single ‘time-averaged’ exposure and examining the modified optical transform fringe pattern.

Introduction to Classical and Modern Optics

Abstract: Preface. 1. Reflection and Refraction. 2. Thin Lenses. 3. Thick Lenses and Combinations of Lenses. 4. Mirrors. 5. Aberrations. 6. Stops and Pupils. 7. Gradient-Index, Fiber, and Integrated Optics. 8. Lens Design. 9. Optical Systems. 10. Systems Evaluation. 11. Interference. 12. Thin Films. 13. Coherence. 14. Diffraction. 15. Diffraction Gratings. 16. Light Scattering. 17. Polarization of Light. 18. Optical Data Processing. 19. Holography. 20. Light Sources and Detectors. 21. Radiometry/Photometry. 22. Absorption. 23. Lasers. 24. Relativistic Optics. Answers to Odd-Numbered Problems. Index.

Zone Plates and Their Aberrations

Abstract: The zone plate is an optical device that depends on interference, not reflection or refraction, for its image-forming properties. Although the irradiance at the focus is only 110 that of a lens with the same aperture, a zone plate with 100 or more zones is capable of resolution equal to that of the lens. Zone plates can be used in spectral regions where conventional optics are unavailable and for special applications in the visible spectrum. This paper derives the third-order and chromatic aberrations of the zone plate. The image may be diffraction limited only if the illumination is relatively monochromatic. Like the pinhole camera, the zone plate turns out not to suffer from linear distortion, even at very wide fields.

Multiple focal contact lens

Abstract: A contact lens construction suitable for use by individuals ordinarily requiring a bifocal prescription. The lens includes a light transmitting area interrupted by spaced-apart opaque portions. Continuous focal characteristics are achieved by utilizing light transmitting portions for providing vision requirements and for achieving a sufficient peripheral field, adequate illumination, and normal centering. A distance vision correction is provided in a centrally located lens area.

Conformational changes in human lens proteins in cataract

Abstract: The reactivity of protein thiol groups in human lens and the susceptibility of the proteins to tryptic digestion were investigated. Both were found to be greater in some cataractous lenses, indicating that lens proteins have unfolded during cataractogenesis. Almost all the tyrosine in the proteins of the normal human lens reacts with tetranitromethane and is therefore probably on the outside of the major lens proteins.

Solid state lamp assembly having conical light director

Abstract: A lens cap is positioned over a light-emitting diode, and a somewhat conical-shaped plastic light director extends between and in intimate contact with the lens cap and the diode, the smaller end of the conical light director being at the diode. A method of manufacture is disclosed in which a viscous plastic monomer is placed in the lens cap and/or on the diode and allowed to deform by gravity to form the conical light director.

Liquid crystal stereoscopic viewer

Abstract: An optical device, useful for three-dimensional stereo viewing not requir any mechanical shuttering, including two liquid crystal lenses, each comprising: (1) a thin layer of liquid crystal material, preferably nematic liquid crystal; (2) two plates of conductively-coated transparent material enclosing the liquid crystal, each plate being connectable to a source of voltage, and each plate being insulated from the other; (3) a front polarizing sheet forming the outside surface of the crystal lens; and (4) a rear polarizing sheet forming the inner surface of the crystal lens. The axes of polarization of the front and rear polarizing sheets are at right angles to each other, with the result that maximum light transmission through each of the lenses occurs when no voltage is applied across the conductively-coated plates, and minimum light transmission occurs when a voltage is applied across the coated plates.

Measurement of the radius of a high-power laser beam near the focus of a lens

Abstract: The flux-time waveform from a mechanically chopped laser beam is used to find a Gaussian pattern approximating to the distribution of energy in the beam. The technique, which is insensitive to errors in locating the beam centre, has been used to measure the minimum radius of a carbon dioxide laser beam having a continuous power of 2 kW focused into a region less than 2 mm in diameter.

Optical measuring apparatus

Abstract: A narrow laser beam is directed towards a mirror which is rotated to effect rotary planar scanning or sweeping of a lens constructed to convert the rotary scanning beam into a parallel scanning beam. An article to be measured is positioned in the path of the parallel scanning beam at generally the focal point of the lens, and the interruptions of the parallel scanning beam, as produced by the article, are sensed by a photodetector. The photodetector transmits corresponding pulses or signals through an amplifier to an edge decoder which receives a reset signal with each pass of the scanning beam. The edge decoder may provide for selecting different combinations of signals received from the amplifier to control the counting of constant pulses received by a counter from a high frequency generator or clock so that the counted pulses correspond to the dimension of the article at the plane of the parallel scanning beam. Preferably, the motor which rotates the scanning mirror is supplied with electrical energy from the clock through a frequency divider, and the amplified signals from the photodetector are compared with a reference level to provide an automatic gain control for the amplifier.

Oculomotor adjustments and size constancy

Abstract: The effect on matched size of the oculomotor adjustments was determined by stimulation and relaxation of accommodation and convergence by means of spherical lenses. The normal coupling between accommodation and convergence was maintained by introducing the amount of convergence appropriate to the lens power and each S’s interpupillary distance. Data indicate that the oculomotor adjustments are adequate to account for size constancy up to approximately 1 m, beyond which their effect progressively decreases. The actual accommodation in force was assessed by means of the laser scintillation technique. It was determined that the magnitude of accommodation responds accurately to the spherical lens introduced up to about 1 m observation distance, beyond which underaccommodation was noted. Examination of the matched size as a function of the actual accommodation distance reveals a very close correspondence to the size constancy prediction up to about 1 m.

Wide-Angle Optical Model of the Eye

Abstract: Several optical models of the eye have been proposed [1–6]. However, in all of them the distribution of refractive indices was taken either from biological or embryological data or from measurements on frozen sections of the lens. The optical performance of these models was a result of this design, and not its basis. Therefore, these models are not suitable for a study of the internal structure of the crystalline lens.

Application of a Fresnel zone plate to gamma-ray imaging.

Abstract: The fundamental principles of holography were first set forth by Gabor in 1948 (7). Rogers de scribed the hologram in terms of a generalized Fresnel zone plate in 1950 (2). In 1961, Mertz and Young realized that a Fresnel zone plate could be used to construct a hologram using incoherent radiation (3). They applied the principle to imaging x-ray stars. This technique has now been applied to imaging gamma-ray sources at the suggestion of Barrett (4). The properties of a Fresnel zone plate are de scribed in almost any elementary optical textbook (5). A zone plate pattern consists of alternating opaque and transparent rings whose bounding radii are in the ratio of the square roots of successive whole numbers. It behaves as a lens with the principal focal length given by

Convex‐Concave Resonators for TEM00 Operation of Solid‐State Ion Lasers

Abstract: Optical resonators with one convex and one concave mirror offer significant advantages for TEM00 mode operation of solid‐state lasers. High efficiency and low sensitivity to perturbations and compactness have been obtained in comparison to other resonator types. The resonators described are characterized by a stability product equal to one‐half, with one g parameter greater than unity. An equivalent resonator incorporating an intracavity lens is also described which offers a focused light beam of a selected radius useful for intracavity modulation or nonlinear effects. Experimental results are given for continuously pumped Nd: YAG lasers.

Optical limited scan antenna system

Abstract: This invention relates to an optical antenna system including an aperture lens, a feed lens and a feed array for scanning a pencil beam or multiple simultaneous beams over a limited angular sector with good sidelobe levels and minimum gain degradation. Both amplitude and phase distributions over the aperture lens are controlled for all scan angles. Also, the feed lens may be positioned in a manner such that virtually the entire aperture lens is illuminated for all scan angles thereby minimizing the size of the aperture lens, energy spillover and rate of gain decrease with angle from boresight.

Surface inspection with scanned focused light beams

Abstract: A surface inspection system uses a highly focused spot of light moved rapidly over the surface to perform an inspection This permits a ready location of the defects, gives some indication as to their size, and permits a high resolution inspection to be performed in a relatively short time An optical arrangement is employed in which a scanned beam is brought back through the same lens system used in generating the scan to produce an immobilized return signal beam A stop or spatial filter is used on the return beam to permit only the light scattered from defects to reach a detector

Arrangement for automatically focussing an optical instrument

Abstract: In an optical instrument for viewing an illuminated object by means of an objective lens first reflecting means are provided for so reflecting a bundle of invisible light rays out of the illuminating light that the invisible light again enters the illuminating light in only one half of its cross section. The invisible light is then reflected back from the object into the respective other half of the cross section of the illuminating light where second reflecting means are provided for reflecting the invisible light onto a differential photoelectric means. A reference mark is arranged in the path of the invisible light before it is reflected from the object and an image of the reference mark is produced on the differential photoelectric means. A voltage is generated by the latter when the reference mark appears on one of the photoelectric elements constituting the differential photoelectric means, this being the case whenever the object is not in focus. A setting mechanism is provided which is actuated by the generated voltage for varying the distance between the object and the objective lens sufficiently for bringing the image of the reference mark into focus again.

Soft contact lens case

Abstract: A case for storing soft contact lenses, usually in a liquid which cleans and sterilizes the stored lenses, comprising a container having a threaded, fluid-tight closure cap, a base plate on the cap insertable in the container as the cap is placed on the container, and two upwardly opening compartments in the base plate for receiving two lenses, each compartment containing a perforated hemispherical lens support that is mounted in the compartment for movement between a lowered, retracted position and a raised, extended position. A hinged cap covers each compartment and is releasably latched in a closed position over the lens support, which is movable to the raised position by means of a push button extending through the underside of the base. A lost-motion connection limits the back and forth motion of each lens support, and the cover cups are held in spaced relation with the base and with the lens supports, when closed, to prevent damage to lenses on the supports.

Wide angle, narrow bandwidth laser detection system

Abstract: A laser detection system for examining a large field of view to determine if the system is being illuminated by laser radiation at a specific frequency. The system includes a first positive lens system for gathering light over a large field of view and for substantially collimating the light for passage through an interference filter. The interference filter allows the passage of radiation in a narrow bandpass region about the specific frequency of laser radiation of interest. Radiation passing through the filter is then condensed by a second positive lens system and directed onto a photosensitive detector. The first and second lens systems form an image of the detector at the entrance to the first positive lens system which defines the entrance aperture to the laser detection system. In the preferred embodiment the first and second positive lens systems each consist of a hyperhemispherical lens and a fresnel lens.

Apparatus for refracting the eye

Abstract: An apparatus for refracting the eye utilizes two separate optical paths to minimize stray light and optical interference. The apparatus includes dual lens means, each disposed along one of the optical paths, for selectively varying the spatial relationship of a beam of radiant energy passing therethrough. The apparatus comprises a source of radiant energy, modulating means for forming a modulated beam of radiant energy, first lens means, projecting means for introducing a portion of the beam into the eye and for receiving and projecting a reflection of the beam from the retina of the eye along the second optical path, second lens means coupled to the first lens means, and analysis means for forming an image of the reflection and determining the sharpness of focus of the image. The modulating means comprises a dual bladed light chopper which presents to the eye an image of a moving slit representing in alternate succession two apparent sources of radiant energy at two spaced apart distances. The lens means are automatically adjusted to achieve optimum sharpness of focus and the magnitude of the correction to the lens means corresponds to the refractive correction required by the eye. Image rotation prisms are disposed along each of the optical paths and together with the analysis means through suitable electronic coupling provide an indication of the presence and magnitude of an astigmatic condition of the eye.

Flashing vehicle warning beacon with lens and reflector

Abstract: A warning beacon that more efficiently distributes light is disclosed. The beacon includes a flashing, largely omnidirectional, central light source, a conical reflector above the light source and an encircling lens system. The light source includes a partly circular, high intensity discharge lamp coaxial with the lens. One of several encircling lenses is selected for the desired beacon characteristics. A convergent lens, resembling, in section, a planoconvex lens, collects light into an encircling aureole of increased intensity emanating from the lens. A reflecting and refracting interior surface will spread the visual source. Fresnel lens sections can be chosen to increase visibility. The reflector diverts ordinarily wasted light. Between the reflector and the lens, light passes up and out to illuminate the beacon's environs. The lens is constructed of segments whose color may differ one from another and from an encasing dome.

Optometric apparatus and process having independent astigmatic and spherical inputs

Abstract: An apparatus and process for measuring optometric spherical and cylindrical optic correction to the eye is disclosed. Typically, two pairs of counter-rotating positive and negative cylindrical lenses are actually used or optically emulated. As actually used, each positive cylindrical lens is counter-rotated relative to its paired negative cylindrical lens. These counter-rotating positive and negative cylindrical lenses produce variable positive and negative cylinder power relative to two axes substantially orthogonal to the optical axis of the lens instrument. Each pair of cylinders is aligned and counter-rotated relative to the remaining pair of cylinders to generate its positive cylinder and negative cylinder along the optical axes at a non-coincident angle (preferably precisely 45* removed) from the corresponding axes of the remaining counter-rotating lens pair. By choosing preselected positions of counter-relative rotation between the paired lens elements of each pair, virtually all optically practical angles and powers of cylindrical lens astigmatism correction can be generated independent of the spherical optical properties of any ocular lens train. Provision is made for the emulation of counter-rotating lens pairs by the insertion of the lens elements having variable astigmatic and spherical powers with the aforementioned optical properties. The process includes a Cartesian coordinate plot for describing astigmatic correction with reduced error, especially at low cylinder power.

Coherent optical multichannel correlator

Abstract: A coherent optical multichannel correlator for identifying an object by permeating an object with a beam of coherent light which is projected through a Fourier transformation lens onto a filter hologram which reconstructs a reference beam projected on a photo detector when the object to be identified corresponds to the filter hologram characterized by providing a plurality of filter holograms arranged on the focal plane of the lens, and a diffraction grating modulator to modulate the light beam to control the selection of the filter hologram on which the light is projected. Modulation can be either by changing the grating constant to vary the angle phi between the diffracted beam and original beam axis or by rotating the orientation of the diffracted beams through an angle theta. Preferably, the diffraction modulating varies both the angle phi and the angle theta either continuously to have the diffracted beam follow a spiral path along the filter holograms or in a step-like manner to have the diffracted beam follow a path of concentric circles along the filter holograms. The modulator can be a pair of rotatable diffraction gratings, a pair of rotatable diffraction gratings which are thin phase holograms, or a pair of diffraction gratings, one being a volume-phase hologram and the other a thin (phase) hologram. The modulator can also be a fixed grating of electro-optical material which has a grating pattern with a grating constant and orientation which are controlled by the application of an electrical or a magnetic field, or some other means that shifts the illuminating beam on an angle phi.

Eye glass frame for replaceable lenses

Abstract: An improved pair of eye glasses in which each lens rim opening of the eye glass frame has a removable upper and lower lens for interchange with other clear or tinted lenses, the present invention including a latch that automatically locks the upper lens from dropping out accidently when the lens frame is opened during lens interchanging operation.

Device for lighting and examining a cavity

Abstract: A device for examining the inside of a cavity and, more particularly, for viewing or photographing the retina comprising a plurality of optical fibres cooperating with a light source, and an optical system forming an image of the cavity lit by the optical fibres. In this device, the optical fibres are mounted along the generating lines of a frusto-conical support, with their transmitting ends distributed over the smaller base of the support, whereas the lens of the optical system are mounted within the support, at right angles to the axis thereof.