Showing papers on "Lens (optics) published in 1971"

The elastic constants of the human lens

Abstract: 1. When the lens is spun around its antero-posterior polar axis in an apparatus designed for the purpose, high speed photography can be used to record its changing profile. By this method a variable radial centrifugal force can be applied to the lens which mimics the pull of the zonule.2. If the lens is not stressed at its centre beyond 100 Nm(-2) it behaves as a truly elastic body. When stressed beyond this limit visco-elastic strain is produced at its poles.3. The human lens has isotropic elastic properties at the extremes of life, but at the other times Young's Modulus of Elasticity varies with the direction in which it is measured.4. Young's Modulus of Elasticity of the lens varies with age, polar elasticity and equatorial elasticity, at birth being 0.75 x 10(3) and 0.85 x 10(3) Nm(-2) respectively, while at 63 years of age both are equal to 3 x 10(3) Nm(-2).5. A comparison of Young's Modulus of the young human lens with that of the rabbit and cat shows that the polar elasticity of the lenses of these animals was 5 times greater in the young rabbit, and 21 times greater in the adult cat. Equatorial elasticities of the rabbit and human lens were equal, while in the cat the equatorial elasticity was four times greater.6. A mathematical model showing the lens substance possessing a nucleus of lower isotropic elasticity than that of the isotropic elastic cortex surrounding it, accounts for the difference between polar and equatorial elasticity of the intact adult lens.7. The implications of these findings are discussed in relation to:(i) accommodation and the rheological properties of the lens;(ii) possible differences in the physical state of the lenticular proteins in the cortex and nucleus which may account for the senile variations in Young's Modulus of Elasticity in these regions of the lens;(iii) the loss of accommodation due solely to an increase in Young's Modulus of Elasticity of the lens between the ages of 15 and 60. This would amount to 44% of the total observed in vivo.

Theoretical Eye Model with Aspherics

Abstract: A model for the human eye is proposed, similar to Gullstrand’s well-known 4-radius model, however with the front surface of the cornea and the back surface of the crystalline lens taken to be rotationally symmetric aspherics. Whereas for the cornea a polynomial is used based on experimental data of Bonnet, a second-order parabola was tentatively adopted for the back surface of the lens. This model results in slight spherical undercorrection, in agreement with experimental findings. On the other hand, the sine condition is not well satisfied, probably due to neglect of the shell structure of the lens. By ray tracing, astigmatism and coma as well as the meridional and sagittal focal lengths were computed up to a visual angle of 90°. Calculations were also made for the same model preceded by a plano-concave contact lens (Goldmann 3-mirror contact glass), showing that this combination results in considerably reduced astigmatism.

Shearing interferometer using the grating as the beam splitter.

Abstract: The theoretical interpretation of the shearing interferometer based on the moire method using the fourier image of the grating is described. To obtain a pattern with good contrast, the observing plane must coincide with the normal fourier image plane of the grating or with the reversed fourier image plane. The information obtained by this method is the first partial derivative and under certain conditions the second partial derivative of the distortion from the reference wavefront, which is planar or spherical. Applications to measurement of the phase gradient and lens aberration are shown.

Optimum design and depth resolution of lens-sheet and projection-type three-dimensional displays.

Abstract: The primary purpose of this paper is to propose a comprehensive optimum-design theory of lenticular-sheet three-dimensional pictures. The proposed theory features the use of depth resolution of a 3-D image as the measure of the 3-D picture quality. The optimum parameters in the picture taking process, the optimum lens pitch and the depth-resolution limitation, are discussed. The obtained results are also applicable to a specific type of integral photography and to the projection-type 3-D display including projection-type holography. It is found that the optimum pitch of the lens sheet or the lens-type direction selective screen ranges between 0.1 mm and 0.5 mm in most cases, whereas it ranges between 0.2 mm and 1 mm for the triple-mirror screen.

Microwave lens antenna and method of producing

Abstract: A microwave lens for use in the transmission of microwave energy, and a method of producing such a lens. The microwave lens of this invention transforms microwave energy passing through the lens to a desired specific phase and amplitude distribution. Both surfaces of the lens are contoured interdependently to provide the desired phase and amplitude distribution.

Light scanning and printing system

Abstract: A light scanning system of controlled spot motion variation perpendicular to the direction of scan utilizing a rotating mirror and two cylindrical or toroidal lenses positioned relative to the rotating mirror to allow increased nominal axis of rotation to facet angular tolerances while maintaining a distinct non-overlapping line scan. Specifically, for one application the axis of rotation of the mirror is orthogonal to the plane formed by the incoming and reflected beam from the mirror. The first cylindrical or toroidal lens, which has little or no power in the scan plane, focuses the incoming beam in the azimuth perpendicular to the scan onto the mirror while the second cylindrical lens acts as a beam configurer to configure the beam to substantially collimated shape while directing it towards a spherical lens for focusing onto an image plane.

Scattering of Light from a Rotating Ground Glass

Abstract: We report some experimental results concerning the statistical properties of a light beam scattered by a rotating ground glass with average-size inhomogeneities of approximately 1 μm. Photocount statistics measured at different scattering angles and for different angular velocities of the ground glass have confirmed the known result that the scattered-light amplitude is a stochastic gaussian variable. The Bose–Einstein nature of the photocount statistics has been verified with an accuracy of a few parts per thousand. Self-beating measurements on the scattered light of a He–Ne laser in a TEM00 configuration have shown that the power spectrum is a gaussian function of the frequency. The dependence of its half-width on the angular velocity of the ground glass and on the focal length of the lens that focuses the beam on the scattering surface has been measured. The experimental results agree very closely with our theoretical predictions.

Oxygen tension under an oxygen-permeable contact lens.

Abstract: The oxygen tension at the anterior corneal surface under an oxygen-permeable contact lens is shown to be a function of the oxygen transmissibility and the thickness of the lens. The oxygen transmissibilities of several gel contact lenses and a silicone rubber lens are reported together with the procedure for making this measurement. Several of the lenses are shown to give, for an open eye, an oxygen tension at the corneal surface sufficient for maintenance of normal corneal thickness. None of the lenses tested will do this for the closed eye.

Laser system for microsurgery

Abstract: A beam of infrared energy from a CO2 laser operating in its lowest order spatial mode is passed through a converging lens and directed to an operating site by a mirror or beam splitter. In order to locate the invisible focused spot of infrared energy a beam of visible light from a He-Ne laser is introduced coaxially into the path of the CO2 laser beam by a removable mirror. In another embodiment the He-Ne beam is passed through a beam splitter to form two parallel channels focused by microscope objectives on the input ends of respective fiber optic light guides. A rotating chopper disc is positioned in front of the light guides to alternately block and pass light in each channel. The other ends of the light guides are connected to marker projectors located above the beam splitter for the CO2 beam, but just out of the field of view of an overhead operating microscope. A lens and mirror system in each projector focuses the visible light through the beam splitter onto the focal point of the CO2 beam at the operating site. If the intended site is above or below the CO2 beam focal point, spaced red dots alternating at the frequency of the chopper disc will appear to the viewer through the microscope, indicating the need for further adjustment. Perfect adjustment is indicated by a single non-flashing dot.

Design of Singlets with Continuously Varying Indices of Refraction

Abstract: The use of a continuously varying index of refraction provides new degrees of freedom in the design of lens systems. By use of the third-order aberration theory developed by Sands, the effectiveness of these new degrees of freedom in correcting third-order aberrations is determined. After the theory is cast into a form suitable for a computer, two major designs are done. The first is a singlet with an axial gradient that is corrected for third-order spherical and chromatic aberrations and has no third-order distortion. A radial gradient is used in a singlet to correct all third-order monochromatic aberrations except Petzval curvature of field. The results of the study indicate that axial gradients have the same effect as aspheric surfaces for third-order aberrations. The study also shows that radial gradients are more effective in aberration correction than axial gradients and have a greater potential in lens design.

Biological effects of microwave radiation.

Abstract: Concern over the possible hazards of cxposurc to microwave radiation has lately been on the incrcase. Increasing industrial and commercial use of microwave generators for heating and cooking, increasing power of radar scts, and expansion of the broadcasting industry have resulted in more widespread interest in the possible biological eKccts of these electromagnetic radiations. A critical review of the literature on biological effects ofmicrowave irradiation is presented along with an analysis of the present status of standards and hazard

Variable‐Focus Liquid‐Filled Hydroacoustic Lens

Abstract: A large fluid lens with accompanying reservoir and pump arrangement is described, with emphasis on its underwater acoustic‐imaging application. Pertinent properties are cited of the neutrally buoyant lens fluid, the elastomeric containment membranes, and the composite lens. The liquid‐filled lens potentially provides better over‐all acoustic transmissivity than does a comparable solid lens and has an equivalent acoustic refractive index. Focusing, achieved without physical motion of the lens proper, occurs in a manner analogous to the operation of the human eye. Introduction or removal of fluid changes the curvature of the lens‐membrane surfaces. Theoretical consideration reveals the stretched‐membrane surface configuration to be approximately spherical. Thus, standard spherical lens equations are combined with appropriate mensuration formulas to obtain lens calibration equations. A hydroacoustic image taken with the liquid lens is displayed. This image is compared with that formed under identical circums...

Drape for operating microscope

Abstract: The microscope drape is fabricated from a very thin, transparent, heat-resistant plastic film which is adapted to completely house an operating microscope including its support arms whereby no air can escape from the interior of the drape except through the open end thereof which is located remote from the microscope. The drape includes an optically clear, distortion free, transparent lens and means for disposing said lens in parallel, enclosing relationship with the objective lens of the microscope. The drape also includes cylinder-defining ocularhousing extensions which include means for securing said extensions to the oculars of a microscope for precluding the escape of air from the interior of the drape by way of said extensions.

Solid state lamp construction

Abstract: A lamp construction in which a lens is positioned with respect to a light-emitting diode element so as to shape the light beam in a desired pattern. An epoxy material, having an index of refraction greater than unity, is placed over the diode element and is provided with a convex meniscus curved surface so as to direct the emitted light toward the lens. The efficiency of the lamp is thus increased by a two-step process: first, the epoxy material causes an increase in the critical angle of the light-emitting diode whereby a greater amount of light is emitted; and, second, the shaped epoxy directs a major amount of the emitted light toward the lens. The invention is economically manufactured, by applying the epoxy in liquid form over the diode element whereupon it hardens and naturally assumes the desired convex meniscus curvature.

Optical system for improved eye refraction

Abstract: Eye refraction optical system including birefringent and variable power lens means in optical alignment with target structure providing target area to be viewed simultaneously in light of two different groups of polarized light rays, said birefringent and variable power lens means including birefringent means for effecting a slightly different dioptric power for the viewed target area for one of said groups from that of the other and also including movable refractive lens means for changing the effective dioptric power of both target areas simultaneously for choice by patient of image of best focus.

Inhomogeneous Lenses, III. Paraxial Optics

Abstract: Formulas for the four gaussian constants A, B, C, and D characterizing the paraxial properties of a symmetric optical system are derived for various single lenses in which the refractive index varies continuously from point to point. Particular attention is paid to those lenses with either a cylindrical or an axial index distribution and questions pertaining to the depth of an axial distribution are considered; in particular, it is shown that the depth of an axial distribution has little effect on the paraxial properties. More general distributions are treated by expanding the gaussian constants as power series in the lens thickness. These results are applied to the problem of estimating tolerances on the inhomogeneities. It is shown that the choice of index distribution can have important effects on the relationship between the power of the lens and its Petzval field curvature.

Bifocal corneal contact lens and method of making same

Abstract: A bifocal corneal contact lens and method of making same wherein a carrying lens or lens body has a corrective optical prescription for viewing distant objects and has a near viewing portion or bifocal segment fused in an indentation of one surface thereof, said near viewing portion having a corrective optical prescription for viewing near objects, the lens body having a predetermined power to correct for distant vision and the segment having a power equal to the exact refractive add of the eye to correct for near vision and having a size in relation to the size of the pupil of the eye so that the optimum focal points of the lens body and segment are spaced apart a distance less than the radius of the eye and actually overlap and blend together to give a clear and continuous image when the gaze is shifted between near and distant objects without any optical jump or fuzziness of vision occurring.

An afocal electrostatic lens

Abstract: The focal properties of a pair of lenses spaced so that the second focal point of one and the first focal point of the other coincide are discussed. It is shown that if the two lenses are identical they form a system with the property of forming an image at a fixed distance from an object and with a magnification that depends only on the overall voltage ratio (as V'/V)-14/). The focal condition which the voltage ratios of each lens must satisfy is shown to be a constant separation of focal points. Calculated focal loci are presented for some equal diameter cylinder lenses.

Correction of optical aberrations by neutron irradiation.

Abstract: The refractive index of optical materials can be modified by means of neutron irradiation. By varying the radiation dose over selected areas of a lens according to some given law, the local change in the refractive index can be adjusted to correct for different types of optical aberrations. The particular case of spherical aberration is treated in detail. It is shown that irradiation leads to index modifications of the required order of magnitude and that irradiation times are acceptable. Moreover, the stability of the index modifications, the possibility of bleaching—without curing the index—and the absence of residual radioactivity make an irradiated lens suitable for optical applications. The optician has thus at his disposal a new parameter.

Flexible refracting membrane adhered to spectacle lens

Abstract: An ophthalmic device for treating or diagnosing an eye disorder comprising the combination of a spectacle lens and a flexible membrane formed of a transparent plastic and having opposed light transmitting surfaces, one of which is planarly smooth for being pressure-adhesively conformed to the ocular surface of the spectacle lens and the other of which has formed therein a plurality of stepped ridges constituting a Fresnel refracting surface which refracts the light transmitted through the lens and membrane in a manner enabling the treatment or diagnosis of the disorder.

Eye tracker and method

Abstract: A technique and apparatus for two dimensional tracking of eye position. An infrared pattern is projected into the eye and measurements taken of the spatial separation of the first and fourth Purkinje reflections, the reflections from the cornea and the back of the eye lens, respectively. Because the centers of curvature of the surfaces of the cornea and lens lie at different distances from the center of rotation of the eye, these reflections move in opposite directions under eye rotation, in either the vertical or the horizontal direction. During translation of the eye in either the vertical or the horizontal direction the spacing or separation between the two Purkinje images does not change. In one embodiment, a rotating scanning disc having a plurality of spaced orthogonal slits is provided and imaging means are provided for imaging the first and fourth Purkinje images of the light source through the orthogonal slits of the scanning disc onto a photomultiplier tube. The time period between pulse outputs of the photomultiplier tube is proportional to the separation of the first and fourth Purkinje images. In another embodiment the two Purkinje images are deflected so as to be incident on photodetectors. The photodetectors and deflecting means are movable so that the two Purkinje images are kept centered on their respective photodetectors. By monitoring the position of the photodetectors and deflecting means an indication is obtained of the separation of the Purkinje images which gives an indication of the orientation of the optic axis of the eye.

Prismatic lenses for lighting fixtures

Abstract: A prismatic lens for an overhead lighting fixture is formed from a transparent material and has a lower face composed of a plurality of arcuate surfaces arranged side-by-side These surfaces form convex magnifying segments or lenticules in the lens The opposite or upper face is composed of a plurality of Vshaped depressions extending downwardly from a generally flat intervening surface The depressions are located behind and centered relative to the arcuate surfaces, whereas the intervening surfaces are positioned directly behind the junctures of adjacent arcuate surfaces The prismatic lens diverts light rays emanating from a light source behind it primarily into zones disposed oblique to the lens so that the intensity of illumination is minimal in the reflected glare zone located directly beneath the lens and in the direct glare zone located generally to the side of the lens, but is maximum in the oblique zones located between the reflected and direct glare zones This distribution provides the most pleasant and comfortable illumination for most visual observations performed beneath the fixture

Panoramic light emitter for warning lights

Abstract: The panoramic light emitter includes a cylindrically shaped converging lens positioned around a central light source. The lens directs the rays of light passing therethrough in a horizontal direction generally perpendicular to the vertical axis of the emitter. Concave reflectors having a configuration in section of segments of a parabola are positioned above and below the cylindrical lens. The light rays strike the reflectors and reflect horizontally parallel to the light rays reflected by the lens so that substantially all of the light from the light source is either deflected by the lens horizontally or reflected by the reflectors horizontally to provide a panoramic source of light for 360 degrees around the vertical axis of the emitter. Another embodiment has a transparent generally cylindrical member positioned over the light source with the axis of the cylindrical member coaxial with the vertical axis of the emitter. The cylindrical member has upper and lower portions positioned above and below the light source that deflect the vertically projected rays of light emanating from the light source to a horizontal direction generally perpendicular to the vertical axis of the emitter. The intermediate portion of the cylindrical member has an annular cylindrical concave lens and annular upper and lower deflectors that also project the intermediate portion of the light generated by the light source in a horizontal direction to thus provide a panoramic source of light for 360* around the vertical axis of the light emitter.

Phased array fed lens antenna

Abstract: A phased array antenna functions as a source of electromagnetic energy directed toward a non-planar lens positioned in the near field of the phased array antenna. The non-planar lens includes a plurality of modules comprised of collector elements, phase shifter elements and radiator elements. Electromagnetic energy radiated from the feed antenna to the plurality of collector elements in the non-planar lens is coupled from the collector elements through the phase shifter elements to the radiating elements. Each phase shifter has a fixed delay which acts upon the electromagnetic energy transmitting through the phase shifter so that the electromagnetic energy radiated by the associated radiating element combines with the radiated energy from the other radiating elements to produce a beam having a modified scan angle relative to the scan angle of the emitted beam from the phased array antenna.

Order Parameter Distribution for the Electrophydrodynamic Mode of a Nematic Liquid Crystal

Abstract: AC electric fields are known to induce a visible domain pattern in certain nematic liquid crystals. We have measured the focal length of the liquid crystal lens system responsible for this visibility. We have also measured the resistance change associated with this electrohydrodynamic mode. These results can be quantitatively interpreted in terms of the director's spatial distribution which is predicted by Helfrich's theory of conduction induced alignment.

Color data acquisition camera

Abstract: This invention is a camera for use in making true color photographs which is especially useful in aerial and space photography applications. In accordance with the invention, the camera provides a gray scale reference image for each scene photographed. This reference image is exposed on an edge of the film by means of a light characteristic reference image negative disposed in close proximity to the film surface and fiber optic light transmission means which transmits light energy to the negative such that the edge of the film is exposed through the reference negative. Edge disposition of the reference image enables automatic processing of true color prints from the negative. The reference image may be made with a light source located in or near the camera and/or with light from the natural or artificial scene-illuminating source. A spot representing the density of the scene being photographed may be exposed adjacent to the one or two gray scale images by light passing through the camera lens and an internal lens system.

Aberration corrected ophthalmic progressive power lenses

Abstract: A novel type of ophthalmic progressive lens of which the one of its two refractive surfaces is a spherical or toric surface and the other of its two refractive surfaces determines with the first mentioned refractive surface a far vision lens portion with a first focal power corrected for the aberrations which are specific to far vision, a near vision lens portion with a second higher focal power corrected for the aberrations which are specific to near vision, and between said far and near vision lens portions, an intermediate vision lens portion with a focal power which progressively varies from said first focal power to said second higher focal power, said intermediate vision lens portion being corrected for aberrations specific to vision of an object point progressively drawing nearer to the lens

Apparatus for boresighting a laser beam emitter device

Abstract: A system for boresighting or aligning the optical axes of a combined infrared laser beam emitter and a low light level television telescope. An optical switch is located in the system where the axes of the telescope and the laser beam are combined, and is effective to divert at least a portion of the laser beam to a lens that focuses the beam on an opaque surface that is capable of being perforated by the laser energy. The opaque surface is backlit, so that after perforation by the laser a bright point of light can be seen in the telescope. If the axes of the laser beam and telescope are aligned, the bright spot will appear at the reticle center of the telescope. If not aligned, the axes are adjusted to produce alignment, or boresighting. The opaque surface is formed on a strip, and an automatic advancing device is operable to advance the strip to present a fresh opaque test surface, upon each boresighting operation.

Electro-optical viewing device

Abstract: An image intensifier tube and power supply elements are rigidly mounted and axially disposed within a housing to form an integral unit. The image intensifier includes a photocathode at one end, emitting electrons is response to light radiation, an intermediate electron multiplier, and a display screen at the other end displaying an image in response to electron impingement thereon. A detachable adjustable focus objective lens mounted at one end of the housing directs light from a source onto the photocathode and a detachable adjustable viewing lens mounted at the other end of the housing provides a view of the image on the display screen. The structure for mounting the objective lens is pre-collimated with the housing and image intensifier to permit interchangeability of lenses. A focus adjustment is provided between two selective positions of the objective lens. Critical collimation requirements can be readily obtained to facilitate use of a binocular arrangement. The mounting structure may also include an adjustable collimating means to provide axial alignment between the objective lens, image intensifier and viewing lens assembly.