Showing papers on "Lens (optics) published in 1968"

Fourier transform photography: a new method for X-ray astronomy

Abstract: In comparison with all other branches of astronomy, X-ray astronomy suffers from a relative dearth of image forming devices. No X-ray lens is known and image formation by reflection requires glancing incidence optics which have small fields of view and are extremely difficult to fabricate, even for the small apertures (about 2 cm2) now employed. The only other imaging device which has been successfully employed is the simplest of all, the pinhole camera. Pinhole cameras with resolutions better than 10−3 rad are easily constructed, but the apertures are very small—not greater than about 10−4 cm2. The new instrument described here is closely related to the pinhole camera and may be viewed as an attempt to overcome the aperture restrictions of this simple device.

Variable power, analytic function, optical component in the form of a pair of laterally adjustable plates having shaped surfaces, and optical systems including such components

Abstract: A plurality of refracting plates, which are generally perpendicular to an optic axis along which they are in tandem, have quintic or higher order surfaces that are relatively movable laterally in such a way as to be substantially equivalent in their different selected positions to a plurality of lens elements having different selected dioptric powers and different selected aspheric powers. This plurality of different refracting plates can perform a zoom function by itself or as part of a system having other lens elements. This zoom function relates to change of focal length and to change of Seidel corrections, particularly spherical aberration.

Optical viewing instrument

Abstract: Microscope adapted to be inserted into the spaces in a living body for direct examination of the interior surfaces thereof and having a magnifying objective lens system, a fiber optical viewing system, eyepiece means for observing the magnified image formed on the rear end surface of said fiber optical viewing system by transmitting the image of the object focused on the forward end surface of said fiber optical viewing system transmitting at high degree of magnification by means of said objective lens system through said fiber optical viewing system to the rear end surface thereof, and fiber optical illuminating system, wherein an optical means having inclined forward end surface is located in front of said magnifying objective lens system so that the optical means easily penetrates into the part to be examined by the microscope, the image of the object contacting the inclined forward end surface of said optical means being focused by means of said objective lens system on the forward end surface of said fiber optical viewing system at high degree of magnification.

Model of refractive-index distribution in the rabbit crystalline lens.

Abstract: The distribution of refractive indices in the crystalline lenses of rabbits was measured with a newly developed optical system. The distribution was assumed to be represented by n=n0-[Z2/A2+(X2+Y2)/B2],where n0 is the index at the center, Z, X, and Y are coordinates, and A and B are constants. Longitudinal spherical aberrations were calculated by ray tracing on models defined by the above equation, and it was found that such a distribution of refractive indices in the crystalline lens plays a very important role in decreasing the spherical aberration and increasing the refractive power.

Ultrasonic imaging techniques and mammograph equipment

Abstract: An improved ultrasonic imaging system specially adapted for examination of a female breast utilizing direct imaging (twodimensional) or holographic imaging (three-dimensional) techniques. Improvements in both types of ultrasonic imaging are described which utilize an improved fluid-filled lens for imaging an ultrasonic field passing through the breast or other object under investigation onto an area detector from which object information may be read out by light. Use of an ultrasonic lens in the reference beam of a holographic imaging system is also disclosed. A technique for holographic imaging wherein viewing optics are focused on the area detector directly instead of upon a focused image in space is also described with improved results under certain circumstances.

Precision Alignment Using a System of Large Rectangular Fresnel Lenses

Abstract: A system of large rectangular Fresnel lenses has been used in the laser alignment system for the SLAC two-mile accelerator. The alignment system consists of a He–Ne laser light source, a photoelectric detector, and the lenses, one of which is located at each of 297 points which are to be aligned. Each lens has the proper focal length to focus the laser to a point image at the detector. When the alignment at a certain point is to be checked, the image from that lens is scanned by the detector. The image is found to be displaced from its normal position by an amount equal to the product of the position error and the magnification of the lens. The alignment sensitivity is ±0.0025 mm. The targets are enclosed in a 60-cm diam evacuated light pipe to avoid atmospheric disturbances.

Microwave Luneburg Lens

Abstract: This article describes a two-dimensional Luneburg lens, fabricated from steps of foam glass of different refractive index as an approximation to a continuous index gradient. This is an improvement over lenses fabricated by assembly of machined parts, which unavoidably contain some air gaps, resulting in different path lengths through the lens. The foam glass lens is superior to a plastic lens since it is able to withstand higher temperatures and hence higher powers, in addition to having superior aging characteristics. Measurements have been made throughout the microwave band, and the results clearly establish the feasibility of this fabrication technique for the construction of a microwave Luneburg lens.

Noncontact measuring probe

Abstract: A noncontacting optical probe capable of giving a continuous reading of the distance from a given reference to a contoured surface. A collimated beam is directed parallel to the optical axis of a fixed objective lens whose optical axis defines a measuring axis. The beam is deviated at a slight angle towards the surface to be measured, with the angle defining a projection axis. A lens assembly focuses the collimated beam to a very small diameter image point in front of the objective lens on the measuring axis. Translation of the lens assembly causes the image point to move along the measuring axis a distance equal to the movement of the assembly. The spot is not defocused along the axis. The light reflected from the surface is collected by the objective lens, directed through a filter and focused towards a prism lying in the focal plane of the lens. The prism is a 90* prism with the faces forming the 90* angle brought to a sharp edge at the focal plane of the lens. The amount of light reflected from the respective surfaces of the 90* angle are detected by photocells. The movement of the lens assembly is measured, and compared with the point at which the amount of light detected by the two photocells is equal and above a predetermined value. The distance from the lens assembly to the surface is measured at this instant. Linear reading can be presented in digital form with a resolution of 0.0001 inch, and to an accuracy of 0.0001 if desired.

Nonfogging transparent material

Abstract: A transparent nonfogging coating is applied to a normally fogging transparent or reflecting substrate. The nonfogging coating preferably comprises a hydrophilic acrylate or methacrylate polymer. The polymer can be modified by copolymerization with a monobasic or polybasic unsaturated carboxylic acid or partial ester thereof. The polymer can be cross-linked with a polyepoxide to increase its hardness. Typical substrates include automobile, train and airplane windows, sunglasses, camera lens, microscope lens, binocular lens, telescope lens, meat wrappers, diving masks, ski glasses, mirrors.

Pattern defect sensing using error free blocking spacial filter

Abstract: Defects in microcircuit patterns are sensed by illuminating the pattern with monochromatic collimated light. The illuminated pattern is imaged through a lens to produce substantially a twodimensional optical Fourier transform of the pattern at a plane on the output side of the lens. An optical filter (transparency) which includes substantially the negative of the Fourier transform of a defect-free specimen of the microcircuit is placed at the aforesaid plane to block the optical frequency components corresponding to the defect-free specimen. Light passing through the filter is processed to provide various indications of the pattern defects.

Lens alignment using gas bearings

Abstract: Disclosed is a device for aligning a lens element on an axis through the center of curvature of the major lens surfaces. The device is characterized in that spherical fluid bearings are used to position the lens so that it can be clamped for rotation about its geometrical axis.

Equivalent-Lens Theory of Holographic Imaging

Abstract: A theory of holographic imaging is formulated in terms familiar from conventional optics. The effects of the curvatures and off-axis angles of the reference and read-out waves are described by equivalent thin lenses and prisms. The formation of the true-image wavefield is found to be completely analogous to the conventional imaging of the object wavefield by the equivalent lenses and prisms. To explain the conjugate image, we introduce the concept of time reversal. The conjugate-image wavefield is the time-reversed object wavefield conventionally imaged by equivalent lenses and prisms (and a plane mirror). The finite size and resolution of the photographic plate are taken into account. The size of the plate determines the effective aperture of the equivalent lenses and prisms, it is equivalent to a diaphragm in the hologram plane. The modulation transfer function of the plate has the same effect as a diaphragm inserted in the imaging bundle during the recording (or the reconstruction) with its center at the reference (read-out) point. The two diaphragms limit the field of view and the resolution.

Spot welding system and method

Abstract: A system and method for microscopic spot welding with laser radiation. The invention, having particular relationship to microscopic multiple spot welding, employs mode selection of laser emitted radiation. A number of objective lenses are positioned in a diverging mode selected laser beam and the lenses are arranged within the spread of the beam in relative geometrical positions corresponding to the number and positions of spots requiring welding. Auxiliary lens means may be employed to direct the diverging laser beam toward the object to obtain proper spacing of the welding spots. The system produces a multiplicity of microscopic welding spots on the object each of a minimum size governed by the size of the Airy disc produced by its respective objective lens.

Eyeglass frame construction for removable lenses

Abstract: READIY CHANGEABLE EYEGLASS LENSES, MORE PARTICULARLY, A FRAME WITH LENS MOUNTING RIMS HAVING INWARD SURFACES RABBETED TO PROVIDE GROOVES EACH HAVING A LEDGE-LIKE LENS SEATING AND BACKING FLANGE. EACH GROOVE FUNCTIONS TO LODGE THE COMPRESSIBLY RESILIENT MOLDING THEREIN. TOP AND BOTTOM PORTIONS OF THE MOLDING ARE RESPECTIVELY PROVIDED WITH A LENS PILOTING AND RETAINING LIP-LIKE GUARD AND A ROW OF PLIANT EAR-LIKE DETENTS WHICH CAN BE FLEXED AT WILL. THE USER CAN POP OUT THE LENSES AND SNAP THEM IN PLACE IN A SELECTIVELY USABLE ALTERNATE FRAME. ONE SET OF LENSES CAN BE USED IN HIGHLY DECORATIVE FRAMES OF UNIQUE SHAPES, COLORS AND DESIGN TO HARMONIZE WITH APPAREL AND COSTUME JEWELRY.

Plural output optimetric sample cell and analysis system

Abstract: Apparatus suitable for receiving a sample for optimetric analysis along with a method of fabricating the apparatus is disclosed. The apparatus includes a sample cell comprising an opaque hollow tubing. A plurality of apertures are defined in the wall of the tubing and a lens barrel which extends beyond the opposite surfaces of the wall is supported within at least one of the apertures. A glass lens is mounted in the lens barrel. A housing is provided with a first channel for receiving the sample cell and a further series of channels extending from the exterior of the housing to the sample cell apertures. A filter element is housed in each of these latter channels. These channels also slidingly receive an excitation light source or a photodetector cell to permit selective focusing thereof. A sample cell containing at least three apertures in the walls thereof can be mounted for rotation relative to a light source or photodetection means for simultaneous or alternate optimetric determination of the components of a single sample. The sample cell is fabricated by supporting a lens barrel within the aperture. A molten portion of glass is deposited in the lens barrel and cooled while in a horizontal position to form a lens having an acceptable angle of 130* to 170* at an aperture of f7 or below.

Reconstruction of a three‐dimensional microscopic sample using holographic techniques

Abstract: A three‐dimensional microscopic sample is recorded holographically using a high numerical aperture but not necessarily perfect lens. The volume sample is reconstructed using the same lens and is viewed using an ordinary microscope. The technique claims a virtually aberration‐free reconstruction image of a volume much larger than that observable with a single positioning of a high magnification objective.

Use of Crossed Cylinder Lens in Photographic Lens Evaluation

Abstract: Two methods are described for testing cameras and camera lenses by utilizing the properties of the crossed cylinder lens, an ophthalmic test device. In the first, the cylinder lens is used in conjunction with a rectangular grid to defocus the star image formed by a collimator. This test permits quantitative determination of axial chromatic aberration, spherical aberration and its variations with wavelength, and coma of the lens. In the second, a segment of the cylinder lens is used as a supplementary lens attachment to the camera, which photographs a polar coordinate chart. Analysis of the photograph permits determination of the sagittal and tangential field curvatures, and also indicates errors in focal adjustment and misalignment of film plane with respect to the lens axis. Since these tests require cylinder lenses of smaller dioptric power and quality superior to that available from the ophthalmic lens industry, methods for the construction and synthesis of large-aperture, weak, cross cylinder lenses and segments thereof are given. Experimental details of the lens testing procedures, together with examples of photographic determination of the various camera and lens defects, are presented. A sensitive test for lateral chromatic aberration is included in an appendix.

A three-aperture electron optical lens for producing an image of variable energy but fixed position

Abstract: An experimental study has been made of the imaging properties of a three-aperture electron-optical lens system. In general this lens has all three aperture potentials different from each other. An apparatus was constructed to determine the potential of the middle aperture required to maintain a constant image position while the potential of the last aperture (and hence of the image) is varied, the object position and potential being kept constant.

Holographic lens with aberration correction

Abstract: A technique for holographically constructing a lens made of stacked Fresnel zone plates on a thick emulsion photographic film which is capable of imaging a wide object field by joining the individual fields of each superimposed Fresnel zone plate to form an unaberrated composite image. The extent of the individual zone plate field is determined by the emulsion thickness and optical construction geometry and thereby allows restriction of this field to a size capable of unaberrated imaging.

Photoelectrostatic copying machine

Abstract: AN AUTOMATIC COPYING MACHINE OPERABLE BETWEEN A REDUCED COPYING MODE AND A FULL SIZE COPYING MODE. IT HAS A TURRET LENS ASSEMBLY MOVABLE BETWEEN DIFFERENT POSITIONS FOR PROJECTING A FULL SIZE OR A REDUCED SIZE IMAGE OF AN ORIGINAL ONTO A COPY SHEET, AND A DRIVE SYSTEM FOR MOVING THE ORIGINAL AND COPY SHEET RESPECTIVELY PAST ILLUMINATING AND EXPOSURE STATIONS AT EQUAL OR UNEQUAL SPEEDS. A RESILIENT OVERTRAVEL OPERATING ASSEMBLY MOVES THE LENS ASSEMBLY BETWEEN POSITIONS AND FIRMLY HOLDS IT IN PLACE. IN THE FULL SIZE COPYING MODE THE COPY SHEET AND ORIGINAL MOVE AT THE SAME SPEED, IN THE REDUCED COPYING MODE THE ORIGINAL MOVES FASTER THAN THE COPY SHEET AND IN PROPORTION TO THE SIZE OF THE REDUCED LIGHT IMAGE. A SINGLE SWITCH CONTROLS THE COPYING MODE. DURING THE REDUCED COPYING MODE, IT TURNS ON EDGE EXPOSURE LAMPS WHICH DISCHARGE UNEXPOSED MARGINAL AREAS WHICH WOULD OTHERWISE FORM DIRTY COPY SHEET EDGES.

A focusing X-ray telescope for use in the study of extraterrestrial X-ray sources in the energy range 20–140 keV

Abstract: We have designed and tested a focusing X-ray telescope with an angular resolution (FWHM) of 1.0° for the study of extraterrestrial X-ray sources in the energy range 20–140 keV. The telescope's lens is an array of rock salt crystals (each of which is approximately one inch square), mounted on a 6-ft-diameter paraboloidal frame. The lens is located 9.5 ft above a 2-in.-diameter NaI crystal and PM tube (which measures the energy of the incident X ray). X rays passing through the salt crystals undergo a 2θ deflection if the Bragg condition for reflection, nλ = 2d sin θ, is approximately satisfied. Optimum thickness and effective energy bandwidths for such reflections have been determined for energies in the telescope's operating range. The area-efficiency product of the lens is approximately 8 times the NaI crystal area from 20 to 40 keV, giving a real improvement in the signal-to-background ratio. Crystals more nearly perfect than rock salt offer the possibility of increased gain over narrow energy intervals...

Electron Energy Analysis by a Cylindrical Magnetic Lens

Abstract: Cylindrical magnetic lenses were developed with the aim of energy analysis of electrons. A set magnetic pole-pieces with rectangular apertures was inserted into the bore of the intermediate lens of a usual electron microscope and was used as an analyzer lens. It has a large chromatic aberration constant for off-axial rays when it was energized to a lens strength k√3. An image of specimen was formed by the objective lens on a slit plane of the field limiting aperture. The energy of electrons which had passed through the slit was analyzed by the analyzer lens and the energy loss spectrum of the limited image was obtained perendicularly to the slit length with an energy resolution of 1 eV at 80 kV. Lens action of the analyzer lens and experimental procedures for energy analysis are described in details. Some results of energy analysis are shown for several specimens of various thicknesses. The energy resolution and position resolution of this analyzer are discussed for a few practical cases.

Strip scanning copying apparatus

Abstract: Strip portions of an original are successively scanned by a row of lenses with toric refractive surfaces having a first radius of curvature in the scanning direction and a second smaller radius of curvature in a transverse direction. The first and second radii are selected so that the image of a part of the scanned strip-shaped portion projected by each lens is reversed in the scanning direction only, and not reversed in the transverse direction of the row of lens means the exposed strip-shaped portions of the copy sheet form together a continuous complete legible image of the original.

An imaging system for EAS optical emission

Abstract: The Cornell University Cosmic Ray Group is pursuing an experimental attack on the problem of detecting and analyzing ultra-high-energy air showers by the optical emission m the atmosphere. A technique has been developed to record pulses of light from a sequence of adjacent positions in the night sky, by imaging a sector of the sky onto a mosaic of photomultiplier tubes nested in the focal surface of a large Fresnel lens. Sixteen such lens units are then necessary to view a full 2π steradians. It is shown that, in the wavelength region 3 400 to 4 500 A, Cerenkov radiation dominates the first 23° from the point of appearance of the shower, while nitrogen fluorescence allows tracking of the shower beyond 23°.

Analysis of phased array lenses

Abstract: An equivalent network representation of a feedthrough lens array, which takes into account mutual coupling between the array elements, is presented. The model is employed to predict performance characteristics, which include element mismatch, peak voltage loading of the phase shifters, element currents, and transmitted power. Both analog and digital phase shifters are treated in the analysis. It is shown that, irrespective of the type of phase shifter, the mismatch from element to element at a fixed scan angle is not identical. This variation is explained in terms of the multiple reflections that take place between the two surfaces of the lens. Further, as a function of scan angle, the element mismatch for a digitally phased array lens does not vary in a smooth manner but exhibits a decided ripple.

Set value indicating apparatus for single lens reflex camera

Abstract: A view finder for a single lens reflex camera is provided in which the exposure data such as shutter speed, lens aperture, distance and the like may be observed; provisions being made to record the data on the photograph. An aperture or window is provided in the camera body for illuminating the data dials. Two pivotable mirrors, a prism and a lens are provided to project an image of the dial data on the border portion of the focusing plate. Both pivotable mirrors are coupled to the shutter release button, the first mirror blocking the incoming light as an exposure is made, the second mirror tilting slightly at the same time. A lamp synchronized with the shutter release button flashing to provide the required light for recording data on the film by the tilted second mirror.

A simplified coherent optical correlator.

Abstract: The basic theory plus a few nonreal time experimental results of a coherent optical analog correlator consisting of only a single transforming lens are given. The two spatial signals to be correlated were written on two side-by-side photographic transparencies (an ultrasonic light modulator may be employed for real time operation). Two types of spatial carriers were used to separate the desired correlation signal from spurious signals in the output diffraction plane. Frequency shift of one input signal may be determined by measuring the spatial shift of the output diffraction pattern.

Process for making plastic multifocal lenses

Abstract: A METHOD FOR MAKING MONOCENTRIC BIFOCAL CONTACT LENSES. THE READING SEGMENT BEING COMPOSED OF A MATERIAL POSESSING A HIGHER INDEX OF REFRACTION THAN THE MATERIAL OF THE LENS AND BEING SEMI-CIRCULAR IN SHAPE AND THE OPTICAL CENTER OF THE READING SEGMENT LOCATED AT THE CENTER OF THE UPPER STRAIGHT EDGE OF THE SEMICIRCULAR READING SEGMENT.

A spectacle-contact lens combination used as a reverse galilean telescope in unilateral aphakia.

Abstract: ABSTRACT The handling of the unilateral aphakic patient is complex. A technique is described that allows the practitioner to take first steps toward restoring binocular vision in suitable cases. A reverse Galilean telescope is partially incorporated in a contact lens placed in front of the aphakic eye. The negative portion of the telescope is incorporated in the spectacle frame. Several problems and fitting details are considered. An outline of the method employed is presented at the end of the article.