Showing papers on "Lens (optics) published in 1974"

Holographic lens and liquid crystal image source for head-up display

Abstract: A head-up display system is disclosed for use in aircraft to display symbols and sensor video. The system uses an array of holographic elements on a transparent plate, or on the inside of the aircraft canopy, as both a collimating lens and a combiner for a light image from a liquid crystal source. An optimum system employs a holographic combiner/lens and a liquid crystal image source, but a holographic combiner/lens may be used with other image sources, and a liquid crystal image source may be used with other collimating lens and combiner arrangements. The thin and flat liquid crystal image source permits its use in an optimum position in the cockpit for both head-up and head-down viewing.

Photorefraction: a technique for study of refractive state at a distance.

Abstract: Photography of the fundus reflections of a point source of light from a human subject facilitates estimation of the refractive disparity about any desired axis, between the plane of focus of the subject’s eyes and that of the camera. The method employs a special attachment to a 35-mm reflex camera, consisting of a fiber-optic light guide mounted in the center of an array of pie-shaped cylinder lens sectors and placed in front of the camera’s wide-aperture lens. The light guide supplies a 1/4 second flash of filtered tungsten light of irradiance less than 1 μW/cm2 at the corneas of the subject, who is seated 1–2 m distant. The reflected light emanating from the subject’s pupils is transformed by the array of cylinder lenses into a star-shaped pattern at the film plane; the lengths of the arms are proportional to the dioptric disparities about the corresponding axes. Theoretical intensity distributions of star patterns for spherical and astigmatic errors have been computed upon the assumption that the retina is a diffuse reflector. They are shown to agree well with experiments. The technique provides an objective method for estimating the refractive states of both eyes of a subject simultaneously, under more-or-less-natural circumstances, and may find practical application in the visual screening of very young children.

Method of removing proteinaceous deposits from contact lenses

Abstract: Proteinaceous material on the surface of contact lenses, especially soft contact lenses, may be removed by contacting the lens for a time sufficient to clean the lens with a substantially isotonic, aqueous solution containing an effective amount of a protease such as papain.

Optical device for producing a minute light beam

Abstract: An optical device for producing a minute beam comprises beam forming means such as laser generator or the like, annular beam forming means such as lens or annular aperture mask for forming the beam from the beam forming means into a beam of annular cross section, and a condenser lens for condensing the annular beam from the annular beam forming means.

Artificial crystalline lens

Abstract: An artificial crystalline lens intended to be attached to the ciliary border area, outside the pupil area, said artificial crystalline lens comprising an optical lens having a supporting leg with a stepped bend intended to be introduced into a hole in the iris for attachment of said optical lens to the ciliary border area. At the opposite edge of said optical lens there is a seam receiving means for attaching said optical lens to the iris.

Speckle-Shearing Interferometric Camera -- A Tool For Measurement Of Derivatives Of Surface-Displacement

Abstract: A camera having a lens with two apertures and equipped with a shearing mechanism is employed to image a specimen which is illuminated by coherent light. With this arrangement, the speckle from one point on the surface is allowed to interfere with the speckle from a neighboring point so that a speckle-grid pattern may be detected in the image plane. By double-exposure or real-time techniques, the speckle-grid pattern corresponding to the deformed state of the specimen is added to the speckle-grid pattern corresponding to the undeformed state of the specimen. The resulting mechanical interference produces a moire-fringe pattern which depicts derivatives of surface-displacements. The camera will be referred to as "Speckle-shearing Interferometric Camera". Three applications of the speckle-shearing interferometric camera are described: (1) mea-surement of slopes of structural deflections, (2) in-plane strain measurement, (3) vibration analy-sis. Experimental demonstrations for each case of the applications are presented. Although the speckle-shearing interferometric camera is based on interferometric principles, it overcomes several of the limitations associated with holographic and speckle interferometries, namely: (1) the setup is simple and does not re-quire laborous alignment of optical components, (2) it does not require stringent mechanical and ambient atmospheric stabilities, (3) coherent requirements of light are greatly relaxed, (4) the sensitivity is greatly reduced, and (5) it does not require differentiation to obtain strains.© (1974) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Focusing Errors in a Collimating Lens or Mirror: Use of a Moiré Technique

Abstract: The Fresnel diffraction pattern of a grating periodically gives an exact reproduction of the grating. By superposing a second grating on such an image, we form a moire pattern that depends upon the degree of parallelism of the incident beam. We present here the possibility of using this technique for studying the focusing errors in a collimating lens or a mirror.

Rear view vision device

Abstract: Compact periscopic device particularly adapted for vehicular rear vision, including an optical train to provide a wide field of view with optimum resolution and brightness and adapted to the confines of a relatively small housing enclosure. The optical train directs the incoming light rays through a series of direction reversals whereby the housing size requirements are considerably reduced. Further, the optical train consists of a pair of alternately operable, Fresnel-type objective lenses of differing focal length to provide for either a wide unit magnification of rear-viewed objects in one instance or a greatly expanded field of view in another instance. The optical train also includes image-reversing and image-inversion reflective surfaces, to correct for lens reversal and inversion of the image.

Computer generated hologram; null lens test of aspheric wavefronts.

Abstract: A major obstacle in using aspheric surfaces in optical systems has been the difficulty involved in accurately testing them. A common method of testing an aspheric optical element is to make a second optical system (null lens or null mirror) that converts the wavefront produced by the element under test into either a spherical or plane wavefront. 1-3 This wavefront is interferometrically compared with a known reference wavefront. In the testing of steep aspherics, the null optics are often expensive to produce accurately. Recent studies showed that null lenses can be replaced with computer generated holograms (CGH). Unfortunately, the CGH required to test steep aspherics are also difficult to produce. It has been suggested that instead of using either a very expensive null lens or a very complicated CGH, often the test can be performed using the combination of a relatively inexpensive null lens and relatively simple CGH. The purpose of this Letter is to illustrate the potential of the combined CGH null lens test by showing the results of a CGH null lens test of the primary mirror of an eccentric Cassegrain system that had a departure

Focusing system for videodisc player

Abstract: A focus detector includes apertured photodetectors which intercept a radiant beam. Changes in focus differentially affect the amount of radiation impinging on the detectors resulting in corresponding changes in their signal output. A videodisc system employing the detector moves a focusing lens to compensate for variations in the position of a target videodisc, so that a scanning beam is always accurately transmitted to a detector. A difference circuit connected to two photodetectors generates a driving signal to energize a lens-moving motor for shifting the focusing lens toward or away from the videodisc.

Integral lens light emitting diode

Abstract: A light emitting diode structure has one or more convex lens formations formed on the surface through which the light issues to provide larger incident angles and reduce internal reflection. Conveniently the structure comprises a multi-layer epitaxially grown structure, and the lens or lenses may be formed integral with the outer surface.

Endoscope capable of changing over the directions of visual field

Abstract: An endoscope capable of changing over the directions of visual field is disclosed which comprises first and second reflecting mirrors arranged in front of an objective lens with their reflecting surfaces opposed and inclined with each other. Either one or both of the first and second reflecting mirrors are made movable so as to selectively effect one of direct sight, lateral sight and rear sight visualizations while observing the interior of a hollow organ or objects not present to the eye.

Wide-angle ophthalmoscope and fundus camera

Abstract: A wide-angle indirect ophthalmoscope contains a contact lens that fits over a cornea and is surrounded by two rings of optical fibers for illumination of the eye fundus. The two rings of fibers are oriented to maximize illumination of the fundus while reducing troublesome reflections. The inside ring is formed of fibers with a numerical aperture and inclination selected to illuminate 100° of the retina. The outside ring of fibers illuminates the periphery of the retina up to 150°. The location and inclination of the rings are calculated to prevent blockage of the entrance pupil of the observation system while avoiding direct illumination of the entrance pupil. A lens series for use in an ophthalmoscope in combination with the contact lens is also disclosed. Further, a fundus camera contains the contact lens, the two rings of optical fibers, and a lens series for use in conjunction with a camera having a 50 mm focal length.

Self-leveling laser assembly

Abstract: Self-leveling light beam projection apparatus for projecting and maintaining a beam of light along a predetermined path relative to the earth's vertical. A housing adapted for mounting in a predetermined plane includes a light source such as a laser generator for generating a collimated beam of light. A lens system including a pendulum mounting at least one lens is mounted for movement about mutually perpendicular axes to seek the vertical and to maintain the projected beam along the predetermined path despite the relative positions of the housing and light source.

Varifocal lens assembly

Abstract: A varifocal lens assembly of a type including at least two lens groups, a first lens group being axially movable parallel to the optical axis of the varifocal lens assembly for varying the focal length of the optical system of the varifocal lens assembly. An automatic focusing device is associated with the varifocal lens assembly to axially move the lens groups as a whole, the other or second lens group or a part of lens elements of the other or second lens group a predetermined distance to compensate for the image shift which takes place during the adjustment of the focal length effected by axially moving the first lens group.

Infections with the therapeutic soft lens.

Abstract: Six of 36 severely diseased eyes wearing soft contact lenses for therapy for at least two months developed corneal infections. An additional two eyes developed severe conjunctival infections. In eyes wearing soft lenses, treatment with corticosteroids and antibiotics should be avoided, if possible.

Photo-electric object detection system

Abstract: A photo-electric light curtain for braking and terminating power to the ram of a press when an obstruction is detected in the curtain area uses an elongated fluorescent lamp as the light source. A number of spaced lens systems arrayed on the opposite side of the curtain area from the lamp focus on spaced points along the lamp. Fiber-optic strands connect the focal point of each of the lens systems with points arrayed about the stationary element of a circular commutator which are scanned by another fiber-optic element having one end affixed to a rotary commutator element and the other end feeding a photodetector. The output signals from the photodetector are processed to detect obstructions along the focal axis of any of the lens systems by fail-safe digital circuitry which provides an output when this blockage is detected for several cycles of the commutator. Counter circuitry, preset by manual switches, allows the system to ignore light blockages caused by permanent installations.

Aberration balancing in rotationally symmetric lenses

Abstract: The expansion of the aberration function of lens systems in analytic form is considered. The results are used to obtain an expansion of the aberration function of a rotationally symmetric system, with either a circular or annular pupil, in a series of orthogonal polynomials. The significance of this for aberration balancing is discussed, and algorithms for obtaining such an expansion numerically are described.

Panoramic photographic methods

Abstract: A panoramic photographic process which employs a photographic instrument having an objective lens with an optical axis, an aperture in front of the lens, and a film guide in back of the lens for travel of film therealong. The method comprises advancing the film along the guide at a predetermined rate of speed, while rotating the instrument about an axis passing through the lens and extending at an angle to the optical axis, the direction and speed of rotation of the instrument being such that the net velocity of travel of the film is substantially zero so that it serves as an instantaneous center of rotation thereby enabling the photographing of the panorama situated above the natural or artificial horizon.

Rotatable head up display with coordinate reversal correctives

Abstract: A rotatable head up display system is provided to furnish target coorindatenformation to the pilot of an aircraft, for example. The head up display may be slaved to a FLIR or TV tracker to display the scene viewed thereby as well as the azimuth with respect to the aircraft. A small cathode ray tube is used for the display and the scene is viewed through a holographic lens so that the display appears at infinity focus. The pilot is also provided with means for controlling the aiming of the sensor (FLIR, TV, or the like).

Method and apparatus for detecting cosmetic defects in opthalmic lenses

Abstract: Method and apparatus for detecting and analyzing cosmetic defects on the surface of ophthalmic lenses. The apparatus according to one embodiment comprises means for scanning a narrow beam of light across the lens surface under inspection together with an array of photodetectors for detecting the manner in which the scanning beam is scattered or deflected as a result of striking a defect on or beneath the lens surface. More particularly, the photodetector array is mounted around the edge of the lens in a symmetrical pattern such that by properly monitoring the outputs of the detectors and by correlating these outputs with the position of the scanning beam, information regarding the position of the defect, the type of defect, and its severity can readily be ascertained in an automatic manner. By properly positioning the detector array around the edge of the lens, the system is able to automatically distinguish between cosmetic defects on the surface being examined and any defects which may be present on the opposite lens surface as well as between actual cosmetic defects and external surface debris such as dust or fingerprints. By an alternative embodiment, the array of photodetectors can be replaced with an array of light sources while the laser can be replaced with an appropriate detector. The system is particularly designed for inspecting the finished front surface of semifinished ophthalmic lenses although it has application in a variety of other fields.

Adjustable mold for direct casting of plastic multifocal lenses

Abstract: Apparatus for finish casting of bifocal ophthalmic lenses from plastic material is described. No further surface grinding or polishing of the lens is required. The portion of the bifocal segment of the lens may be adjusted to any desired location relative to the optical center of the distance field of the lens. The apparatus comprises a power mold having a predetermined spherical or sphero-cylindrical surface, a bifocal mold having a predetermined optical curvature with a bifocal segment having a different optical curvature countersunk in the face thereof, and an annular gasket coupling the power and bifocal molds. The bifocal segment is adjusted relative to the optical center of the cast lens by use of a wedge member. An illustrative calculation to determine placement and thickness of the wedge for a given ophthalmic prescription is set forth. Alternative means for adjusting the bifocal segment by sliding the assembled power mold and gasket relative to the bifocal mold is also described, as is a means for introducing corrective prism into a cast lens.

Holographically generated lens.

Abstract: A holographic lens has been made that utilizes some of our earlier work on holographic aberration correction [ J. E. Ward D. C. Auth F. P. Carlson , Appl. Opt.10, 896 ( 1971)]. The lens properties are obtained by interferometrically recording a plane wave and a pinhole generated spherical wave. The theoretical analysis is followed by the results of the Ronchi lens test, Fourier transformation of a grating, and imaging of a test picture.

Noncontact surface profilometer

Abstract: An electrooptical sensor is described for providing an output proportional to the surface profile and the first derivative of the surface profile in a noncontacting manner. A narrow, collimated laser beam is scanned across the surface of the article to be measured. The scanning laser beam is produced with a uniformly rotating mirror and a lens, and the scanning beam is nominally perpendicular to the surface of the article being measured. The laser beam reflected by the surface is collected by a lens and focused onto a photoelectric position sensor. The output of the position sensor is proportional to the first derivative of the article surface profile. Since this first derivative will in general include a component originating from the tilt of the article surface relative to the scanning laser beam, means are provided for separating this effect from the intrinsic surface slope. By electronically integrating the first derivative output, an output representing the surface profile is obtained.

Adjustable micrometer stage

Abstract: An improved mount for an optical lens or similar device for achieving X-Y adjustment which includes four diametrically opposed 90° spaced knife edges on a lens ring opposed on one side by a spring and on the other side by a micrometer adjustment to provide positive control in the X and Y directions, each motion being independent of the other.

Thermostatically controlled non-tracking type solar energy concentrator

Abstract: A solar energy concentrator comprises an array of cylindrical Fresnel lenses, all of which are fixedly aligned in the East-West direction. Each lens concentrates the sun rays and forms a line image which extends in the East-West direction. Located below the lenses are individual fluid channels which extend in the EastWest direction and are spaced apart in the South-North direction. Each line image focuses onto preferably not more than two of the channels which absorb heat of the concentrated sun rays. Each channel has a thermostatically controlled valve which controls fluid flow through the channel to take place only when the channel''s temperature and/or the fluid therein exceed a threshold temperature level.

Auto-focus camera with solid state range finder

Abstract: An auto-focus camera includes a range finder device having no moving parts. First and second stationary lens devices receive radiation from an object along two spatially separate paths. First and second sensing devices, each comprising a plurality of photo-responsive elements, are arranged to receive the radiation passing through the first and second lens devices, respectively. The first and second sensing devices provide electrical signals representative of the relative position of the intensity distribution of the radiation passing through the second lens device and falling on the second sensing device with respect to the position of the intensity distribution of the radiation passing through the first lens device and falling on the first sensing device. A detecting circuit connected to the first and second sensing devices provides an output signal indicative of that of a plurality of predetermined zones in which the object is located. The camera further includes a control circuit responsive to the range finder output signal for moving the objective lens in the camera to a position at which an image of the object is properly focused on a light sensitive film within the camera.

Plural magnification copying apparatus

Abstract: The disclosure is directed to a copying apparatus permitting copies of originals at a plurality of magnifications. Image rays from an original to be copied are directed onto a first mirror assembly, to a second mirror assembly, through a lens to a fixed mirror, and onto an exposure surface, the exposure surface, and first and second mirror assemblies being moved in the same direction at speeds which are in definite ratios. The second mirror assembly and lens may each be set to different initial positions, to produce different lens to original and lens to exposure surface ratios, and, depending on the initial settings of the lens and second mirror assembly, the first and second mirror assemblies are driven at different speed ratios relative to the speed of the exposure surface.