Showing papers on "Lens (optics) published in 1975"

Optical display systems utilizing holographic lenses

Abstract: This invention is applicable to display systems, such as in a helmet mounted display or a head-up display, utilizing a holographic lens operating at a relatively large off-axis angle in order to perform the dual function of a combiner glass and an eyepiece. The holographic lens is used in conjunction with more conventional optical elements (lenses, mirrors and prisms) to present a high quality collimated virtual image of an object, such as the face of a cathode ray tube, to an observer. The aberrations inherent in a holographic lens constructed to operate at a large off-axis angle and with a large field of view are corrected both by constructing the holographic lens with aberrated wavefronts and by the optical elements used in conjunction with the holographic lens during playback. Some arrangements of the playback systems of the invention include a relay lens having cylindrical surfaces and tilted and/or decentered elements used to compensate for the axial astigmatism and axial coma in the holographic lens. The holographic lens is constructed with aberrated wavefronts primarily in order to correct a large assymetric variation of astigmatism across the field of view which arises because of a difference in tilt of the two image fields corresponding to the two mutually orthogonal line focal surfaces. The tilts of the two image fields are adjusted relative to one another in such a way that they may both be matched by a single tilt of the object surface. The invention herein described was made in the course of or under a Contract or Subcontract thereunder with the Department of the Air Force.

Holographic Optical Elements

Abstract: This article is a survey of the characteristics, technology and applications of Holographic Optical Elements (HOEs), considered as general elements in an optical system HOEs function by diffraction of light from a generalized grating structure with nonuniform groove spacing HOEs provide a system of thin film optics They are capable of unique system functions and configurations, show a rapid variation of optical power and image characteristics with wavelength, have relatively large amounts of astigmatism and coma, and require special consideration of optical efficiency during system design Comparison of the aberrations of specific, f/33 elements shows that the on-axis HOE and the conventional glass lens element have similar aberration levels, while the off-axis HOE has four times as much astigmatism and twice as much coma We show that these grating aberrations, which appear for conjugate points that are different from the HOE construction points, are proportional to the average surface grating spatial frequency of an off-axis HOE HOE technology is similar to conventional optics technology, but is less developed The relative complexity of optical systems with HOEs, and the lack of a suitable aberration theory, produce a relince on computer-based raytracing for system design and development We give the basic raytracing equations and discuss the special requirements for hologram recording appara-tus and materials In applications, HOEs will usually provide unique capabilities rather than replace conventional elements, and will usually operate over narrow spectral bandwidths The use of HOEs in several types of laser optical systems, and in visual displays, appears to be not only advantageous, but also technically and economically feasible

Instant electronic camera

Abstract: A conventional lens system projects an image on a planar array of light sensitive elements of a charge coupled device from which digital signals containing the picture information are produced and stored for reproduction by a mechanical printer.

The optical design of intraocular lens implants.

Abstract: Intraocular lens implants have been around for more than 25 years. On the verge of a major breakthrough to ever widening popularity, there is, however, a general lack of understanding of the pertinent optical principles. A critical comparison is made between this new method and conventional methods of correcting aphakia. From this it appears that the visual needs of the patient are a decisive factor in the selection of the method of correction. Moreover, the full potential of intraocular lens implants can only be realized by appropriate selection of the power of the implant in each situation. To this end, ultrasonic measurement of the ocular axial length is indispensable. The use of standard power lens implants is inadequate. Formulas are presented to make an eye emmetropic or to give it any refractive error. Guidelines are given for the use of these formulas. Two methods for obtaining equal image size in unilateral antiphakia are described.

Dimensions of the human eye relevant to radiation protection (dosimetry)

Abstract: An attempt has been made to clarify the two most important issues relevant to personal eye dosimetry. This involves the identification of the cells which are most at risk from radiation and the specification of their position in the eye. A survey of the radiobiological literature concerning animals and humans shows that the epithelial cells in the equatorial region of the lens are those which are involved in radiation cataract induction. The depth of these cells has been evaluated in the human eye by means of geometrical construction. The relevant dimensions have been determined from a survey of published anatomical data and supplemented by new data obtained by slit-image photography. In a normal adult population (20-65 years) the minimum depth of the incriminated cells is 2.3 plus or minus 0.4 mm; the upper and lower values are associated with young and old subjects respectively. Approximate calculations for isotropic 90Sr/90Y and 106Rh beta-radiation fields indicate that a planar dosemeter, which integrates the tissue dose between depths of 2.5-3.5 mm, should give a reasonable measure of the mean equatorial dose for the variety of eye and irradiation geometries likely to be met during a life-time exposure. The long established, but tentative, value of 3 mm for the effective depth of the lens is thus confirmed.

Observation of protein diffusivity in intact human and bovine lenses with application to cataract.

Abstract: Using the technique of optical mixing spectroscopy, we have observed the Brownian movement and measured the diffusivity of proteins within whole, intact human and bovine lenses. The magnitude and the temperature dependence of the protein diffusivity in bovine and normal human lenses implies that cold cataract is the result of a first-order phase separation of the protein-water mixture in the lens. The magnitude of the diffusivity of proteins within cataractous human lenses indicates the presence of large aggregates of proteins.

Electrostatic lens to focus an ion beam to uniform density

Abstract: A focusing lens for an ion beam having a gaussian or similar density profile is provided. The lens is constructed to provide an inner zero electrostatic field, and an outer electrostatic field such that ions entering this outer field are deflected by an amount that is a function of their distance from the edge of the inner field. The result is a beam that focuses to a uniform density in a manner analogous to that of an optical ring lens. In one embodiment, a conically-shaped network of fine wires is enclosed within a cylindrical anode. The wire net together with the anode produces a voltage field that re-directs the outer particles of the beam while the axial particles pass undeflected through a zero field inside the wire net. The result is a focused beam having a uniform intensity over a given target area and at a given distance from the lens.

The emmetropic and the iseikonic implant lens: computer calculation of the refractive power and its accuracy.

Abstract: The preoperative calculation of the power of a lens prosthesis and the resulting aniseikonia is given, as well as diagrams for reading the emmetropizing and the iseikonizing power of the lens. The consequences of an inaccuracy in the measurement of the dimensional and refractive properties of the eyes are calculated. It can be concluded that the main determinant for an accurate prediction of the power of the intraocular lens prosthesis is the axial length measurement. Since this measurement is carried out by means of ultrasound biometry, it is necessary to emphasize the adequate application of this technique. The problem as to whether an emmetropizing, or an iseikonizing lens should be implanted may be solved with the data supplied by the computer program. A flow chart for this program is given in an appendix.

Catoptric lens arrangement

Abstract: Improved catoptric lens arrangements are shown wherein a beam may be formed from light emitted by a plurality of sources of light, the intensity and direction of such beam being automatically controlled in response to the speed and direction of travel of a motor vehicle carrying such arrangements.

Solar energy apparatus

Abstract: A solar energy apparatus for gathering and transmitting solar radiation to an energy storage area. Wide-angle lens apparatus is used to focus solar radiation on an end of an optical fiber bundle. The other end of the optical fiber bundle is placed in the energy storage area and has a radiating device attached thereto to more efficiently remove the solar energy from the optical fiber bundles. A heat sink is advantageously utilized as a storage means for the solar energy thus gathered and transmitted.

Light emitting device mounting arrangement

Abstract: A mounting scheme designed to provide enhanced brightness and off-axis viewing of a discrete light emitting device is described. The device is placed within a cavity with reflecting side walls. Situated above the cavity is a contrast filter which has formed therein a plurality of spherical lenses. The lens arrangement is designed to produce an array of discrete images of the device separated by dark areas in order to increase the visibility of the device. The cavity side walls reflect onto the lenses light which would not normally be incident thereon thereby further enhancing visibility and permitting good off-axis viewing.

Equator-plus camera.

Abstract: A new fundus camera can photograph a field extending anterior to the equator (148 degrees from the nodal point). The problems of reflection from the surfaces of the crystalline lens are minimized by fiber optic illumination from carefully chosen locations on the cornea. The camera may be used with monochromatic light of various wavelengths and is equipped with interference filters.

Solar heat collector

Abstract: A solar heat-collecting structure comprises a series of interconnected transparent lenses forming a dome-shaped roof for receiving direct solar radiation and for transmitting such radiation through the lenses into the enclosure formed thereby and focusing it on a shallow tray of water forming a floor of the enclosure. The inner surfaces of the lenses are coated with a solar radiation-reflective film so that radiation reflected from within the enclosure toward the roof is re-reflected toward the heat-collecting water surface. Means are provided for removing heated water from the tray and replacing it with water to be heated. Each lens in the roof lens system has a focal length dependent on its position on the roof with respect to the water surface so as to concentrate solar radiation at the water surface and thereby maximize the heating effect of such solar radiation in various sun positions.

The Principles and Practice of Correcting Astigmatism with soft Contact Lenses

Abstract: The principles of correcting astigmatism with soft contact lenses have been discussed and the clinical performance of four different toric soft lens designs reported. Front surface toric lenses performed better than back surface toric lenses. Some of the more obvious problems to be avoided are tight fittings, unnecessarily thick lenses, truncations that are too remote from the lids and lenses that are too small. The effects of differential lens flexure in two meridians were found to cause significant errors if ignored. Toric soft lenses are considered now to be a successful, established clinical entity and it is thought that they will be prescribed with increasing frequency. The role and value of a trial set was also discussed.

Acousto-optical data input transducer with optical data storage and process for operation thereof

Abstract: The present invention is directed to the improvements in an apparatus for holographically recording data on a storage medium with the data being block-organized holographic data by spatially modulating a laser beam into a plurality of object beams which are directed at a storage medium to interfere with a reference beam to form the holographic recording. The improvements are that the means for spatially modulating comprises an acousto-optical light deflector having a large area, piezoelectric sound transducers disposed on the one side thereof, the sound transducer having n electrodes spaced thereon to form n transducer units which receive a signal with a frequency mixture of m frequencies to deflect the beam passing through each unit into m beam directions with the light frequency of each beam having a Doppler shift associated with the amount of deflection. The apparatus also includes providing a lens raster consisting of n times m lens elements arranged in a manner to widen each of the object beams to illuminate the entire hologram and means for compensating for the Doppler shift in the light frequencies of the object beams.

Roof-lens solar collector

Abstract: An array of linear lenses is used as a combination roof-skylight-solar collector. The lenses are oriented at a given latitude to face the most remote of the earth's poles inclined by the local latitude angle. Moving absorbers are used to receive the sunlight at the focal spot of each lens. The absorbers move back and forth during the day as the sun's position changes, causing the focal spots to move.

Photochromic light valve

Abstract: A lens having an optical density which is variable under differing light conditions can be produced by imbibing a synthetic polymer lens such as a polycarbonate or diethylene diglycol bis allyl carbonate polymer with a solution of a metal dithizonate. A polarizing sheet can be laminated thereto or alternatively, a passive dye can be utilized on the inner surface of the lens to provide non-variable reduced optical density in the assembly.

The coupling of light‐emitting diodes to optical fibers using sphere lenses

Abstract: The use of a truncated sphere of high‐refractive‐index material is proposed as a lens designed to improve the coupling efficiency between a light‐emitting‐diode source and an optical fiber. A method of calculating the coupling efficiency for such lens systems is described. Numerical results for the variation of efficiency with lens parameters are presented and discussed for coupling to a fiber bundle with a numerical aperture of 0.14. Improvements of two orders of magnitude in the coupling efficiency over that attainable with the close coupling geometry are predicted.

Large screen video display systems and methods therefor

Abstract: A large screen display system for video modulated collimated light provides superior contrast and brightness, in a shallow depth configuration if desired. A single modulated laser beam which may have different color components is raster scanned, defining a beam envelope which is then expanded along an adequately long optical path length within a confined volume and directed toward a display screen on which the beam impinges. The optical system may selectively redirect the available light energy into a viewing volume with optical gain and with high contrast. In a particularly compact example of a rear projection system, the optical path is defined by successive reflecting elements adjacent and substantially coextensive with the screen, which cause the beam path to traverse behind the screen in successive path segments. The beam envelope is then directed obliquely against the display plane, but differentially redirected so as to be transmitted orthogonally outwardly. Optical gain may be further improved by an array of lens elements at the display plane defining diffuse point light sources to an observer, and the lens elements further may anistropically shape the far field distribution of the light. Light absorbing means disposed at the display plane can be used to enhance color contrast substantially.

Ultrathin coating by plasma polymerization applied to corneal contact lens.

Abstract: Plasma coating (deposition of polymer under the influence of plasma) is utilized to modify the surface properties of corneal contact lens An ultrathin layer (thickness of roughly 200 A) of plasma polymer of acetylene/H20/N2 is applied to poly(methyl methacrylate) (PMMA) corneal contact lenses The surface becomes highly wettable with water compared to uncoated lens When coated and uncoated contact lenses are placed on rabbit eyes, a remarkable difference in accumulation of mucous matter is observed With the control lenses, the accumulation of mucous matter in a week is sufficient to affect the optical clarity of the lenses, whereas the coated lenses show no change after three months continuous wearing The comparative degree of adhesion of the corneal epithelium cells onto glass, modified glass, PMMA, and coated PMMA surfaces is studied using tissue cultures and phase contrast microscopy The coated PMMA surface exhibits a degree of tissue adhesion lower than that of control PMMA and higher than that of glass surface, and no sign of toxicity of the coated surface is observed by the tissue cultures

Light beam shape control in optical measuring apparatus

Abstract: A narrow collimated light beam, such as a 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 interruptions of the parallel scanning beam, as produced by the article, are sensed by a photodetector. The photodetector controls transmission of pulses or signals to means for counting pulses produced by a high frequency generator so that the counted pulses correspond to the dimension of the article at the plane of the parallel scanning beam. In this invention a lens is positioned in the path of the light beam and changes a narrow substantially round light beam into an elongate or substantially flat light beam which is scanned across an object for measurement thereof. The greatest dimension of the light beam is substantially normal to the direction of scan movement. Thus, if there should be irregularities or small particles of foreign material upon the surface of the object or adjacent thereto, the entire light beam is not completely interrupted by such particles or by such irregularities. Thus, a light beam is received by the photodetector in accordance with the average dimension or contour of the object at the measured portion thereof. Thus, the dimension of the object is measured without consideration of small irregularities or small or minute particles of foreign material or the like which may be present upon or adjacent the object at the measured portion thereof.

Multiple image camera

Abstract: Apparatus for receiving video output from a patient scanning device and photographing a plurality of video displays sequentially in multiple images onto a sheet of x-ray film. A video monitor adapted for connection to a scanning device, such as a gamma ray or ultrasonic imaging system, and having a display tube mounted in a housing in spaced relation to a wide angle lens formed to project the image of the face of the display tube onto a sheet of film supported in a film holder mounted on the housing. The positioning of the image on the film is determined by the vertical and lateral positioning of the lens relative to perpendicular X and Y axes corresponding to the length and width of the film. The lens is provided with a shutter for controlling the passage of light therethrough, and a pair of reversing electric motors are provided for selectively positioning the lens along the X and Y axes. Movement of the lens to the desired positions is controlled by light-emitting and light-sensitive pairs, such as a light-emitting diode and a photoelectric diode, connected to the drive motors for actuating and halting same in response to the passage or blocking of light therebetween.

Fish eye lens system

Abstract: An extremely wide angle or fish eye lens system is provided capable of compensating for lateral chromatic aberration, field curvature and astigmatism while providing an aperture ratio of F/4 for use with a compact single lens reflex camera. The fish eye lens system includes a first lens group of four lenses on the object side of a diaphragm and a second lens group of at least three lenses on the image side of the diaphragm. From the object to image side, the first lens group includes a pair of negative lenses, a cemented doublet and a positive fourth lens having a convex surface on the image side adjacent a concave surface of the cemented doublet. The second lens group includes a pair of cemented doublets as two of the three lenses.

A determination of the velocity of ultrasound in cataractous lenses.

Abstract: The velocity of sound determinations made in this study are the result of measurements accurate to 0.5 m/sec. The velocity of sound in a series of 50 cataractous lenses was found to be an average of 1,629 m/sec, 11 m/sec slower than that of normal adult lenses. The velocity of sound found in a smaller series of child lenses was 1,659 m/sec, 30 m/sec faster than the cataractous adult lens. It is postulated that this represents a trend of decreasing velocity of sound in the lens with increasing age.

The microscopic protein structure of the lens with a theory for cataract formation as determined by Raman spectroscopy of intact bovine lenses.

Abstract: Intact bovine lenses have been studied using the polarized Raman spectroscopic technique. A brief theoretical and experimental review of Raman spectroscopy is presented. From the dependence of the Raman depolarization ratio on the propagation direction of the incident radiation we have determined that the uniaxial qualities of the lens result from microscopic anisotropy and have established the quantitative positional correlation of specific chemical bonds with respect to the lens optic axis. In particular, the hydrogen bonded linear CONH groups of the antiparallel ..beta..-pleated sheet are preferentially oriented in directions orthogonal to the lens optic axis. The Raman spectra of intact lenses do not exhibit bands at positions characteristic of either the ..cap alpha..-helix or the random coil protein structure. The antiparallel ..beta..-pleated sheet protein microstructure and the lens fiber cross-sectional macrostructure exhibit a remarkable similarity. This similarity may be causal and is consistent with the protein concentration of the lens, the birefringent properties observed by both Lenhard and Brewster, the CONH bond angle distribution with respect to the optic axis, and the lens anatomy. It is suggested that cortical cataracts are caused by fluctuations in protein orientational order. (auth)

Design and optimization of magnetic lenses and deflection systems for electron beams

Abstract: Methods are described for computing the optical properties of any combination of magnetic lenses and deflection yokes, including the most general case in which the lens and deflector fields may be physically superimposed. These techniques can handle either toroidal or saddle deflection yokes, wound on either nonmangetic of ferromagnetic formers, and can handle cases where the magnetic materials of the lenses directly influence the deflection fields. The basic program for calculating the properties of any given lens and deflection system has been combined with an optimization program, which systematically searches (subject to given physical constraints) for the arrangement which minimizes the deflection aberrations for any specified field size and aperture angle. Illustrative computed results are presented. It appears that conventional postlens single‐deflection systems can have better properties than conventional prelens double‐deflection systems. However, the performance of double‐deflection systems can be improved dramatically by placing the second yoke inside the lens and rotating it relative to the first yoke. An arrangement has been found, which, at the corners of a 5×5‐mm deflection field with 0.005‐rad aperture and 1 in 104 beam voltage ripple, produces a total aberration disk of 0.45 μm before dynamic corrections, or 0.15 μm after dynamic corrections. The properties of in‐lens single‐deflection systems have also been investigated. Such systems offer the possibility, for the same operating conditions as quoted above, of producing a total aberration disk of less than 0.2 μm after dynamic corrections. By introducing a ’’predeflection coil’’ before the main deflection coil, this value can be reduced to less than 0.1 μm.