Abstract: A method for recognizing the presence of a particular target in a field of view which is target position, rotation, and intensity invariant includes the preparing of a target-specific invariant filter from a combination of all eigen-modes of a pattern of the particular target. Coherent radiation from the field of view is then imaged into an optical correlator in which the invariant filter is located. The invariant filter is rotated in the frequency plane of the optical correlator in order to produce a constant-amplitude rotational response in a correlation output plane when the particular target is present in the field of view. Any constant response is thus detected in the outputThe U.S. Government has rights in this invention pursuant to Contract No. DE-AC04-76DP00789 between the U.S. Department of Energy and AT&T Technologies, Inc.

Abstract: An optical device for use in forming a holographic record, comprising a polarizing beam splitter and a spatial light modulator arranged to derive from an incident beam a focussed image beam and a collimated reference beam, the device being of unitary construction and providing substantially equal path-lengths for the image and reference beams.

Abstract: Optical systems, using volume holographic elements (gratings) having geometries which tailor the spatio-temporal dispersion of the optical pulses for the system. The input optical pulse is characterized by a frequency variation across the temporal profile of the pulse. The various frequency components of this pulse are first dispersed by at least one grating which may be of the blazed reflection or holographic volume transmission type. The resultant dispersed light is then diffracted by a holographic volume grating which imparts the desired temporal dispersion characteristics to the pulse. The shape of the holographic element will vary according to the input pulse frequency profile as formed by varied chirping techniques. A grating stage may then be repeated, preferably with additional elements in mirror symmetry to the first or by retro-reflection, in order to recombine the spatially dispersed pulse components into an exiting pulse which may be of vastly compressed temporal profile.

Abstract: An optical substantially afocal beam expander has a negative lens element spaced from a positive lens element. The lens elements are of different materials with respective coefficients of refractive index change with respect to temperature such that the effect of a temperature change on one element is at least partially compensated by the effect of the temperature change on the other element. The beam expander is therefore substantially athermalised with respect to afocality.

Abstract: An interference filter, also referred to as a notch filter, of the type which reflects a certain wavelength range while letting pass over wavelengths bands of a range is disclosed. The filter is designed for operation in the visual and infra-red regions of the electromagnetic spectrum and in the disclosure the uniform layer pairs of material are such that the optical thickness of each layer of the or each layer pair deposited on a plane light-transmitting substrate is a non quarter-wave unequal thickness with respect to its complementary layer. Each layer pair has an overall optical thickness adding up to in total a half-wave thickness.

Abstract: An optical system having a grating lens assembly including a first grating lens which diffracts rays of a beam incident thereupon so as to provide non-parallel diffraction rays and a second grating lens which converges the non-parallel diffraction rays at a predetermined point substantially without aberration.

Abstract: A display source emits light. A first hologram receives the light from the display source and diffracts the received light. The light from the display source is applied to the first hologram at an incident angle A1 and moves from the first hologram at an outgoing angle B1. A second hologram receives the light from the first hologram and diffractively reflects the received light. The light diffractively reflected by the second hologram forms an image of the display source in viewer's field of view. The light from the first hologram is applied to the second hologram at an incident angle A2 and moves from the second hologram at an outgoing angle B2. The first and second holograms are nonparallel to remove a ghost image of the display source which would result from at least one of surface reflections at the first and second holograms. The first hologram has an angle .theta. relative to the second hologram. The angles A1, B1, A2, B2, and .theta.

Abstract: A transparent article comprising a base, at least four coated layers, and a top protective layer is disclosed. The coated layers include a first dereflecting region, a transparent layer of silver or other metal, and a second dereflecting region comprising a layer of titanium dioxide and a layer of another dielectric mater. A titanium dioxide layer may also be a component of the first dereflecting region. Each dereflecting region that includes a titanium dioxide layer also comprises a layer of a transparent oxide or other dielectric material having an index of refraction intermediate between about 2.7, the approximate index of titanium dioxide, and the index of the nearby base or top layer, respectively. The intermediate index material is preferably zinc oxide because this material can be relatively quickly and inexpensively deposited by reaction sputtering. Also disclosed is a method for depositing the coated layers by sputtering and reactive sputtering of titanium and silver, zinc or other materials.

Abstract: A selective light transmissible film or sheet having excellent anti-fogging properties, produced by forming a thin film of a metal and/or a metal compound having transparency and infrared ray reflective characteristics, on the surface of one side of a cellulose derivative film or sheet of which the surface of the other side is saponified with an alkaline aqueous solution, or on the surface of one side of a cellulose derivative film or sheet of which both surfaces are saponified with an alkaline aqueous solution.

Abstract: The invention is a window for transmitting infrared radiation for use with infrared systems, such as an infrared laser. In detail, the window comprises a polycrystalline silicon substrate doped with between 1.times.10.sup.14 and 1.times.10.sup.16 atoms per cubic centimeter of an n-type impurity. The impurities can be selected from the group consisting of Phosphorus, Arsenic, Antimony, Bismouth and Lithium. To reduce reflection, both sides of the sheet are coated with an antireflection coating. Sheet resistances of less than 25 ohms per square are obtainable while simultaneously providing excellent transmission in the infrared at both room and elevated temperatures. The internal heating produced by coupling the window to a source of electrical power can be used for deicing.

Abstract: A gradient index filter can be fabricated with integral antireflection properties without degrading the inband performance of the filter. The filter is for placement between an incident medium and a substrate to reflect incident electromagnetic energy having wavelengths within a predetermined band of wavelengths and to transmit incident electromagnetic energy having wavelengths outside of the reflection band. The filter includes an antireflecting portion having a nominal refractive index profile selected to reflect a minimum amount of electromagnetic energy from a theoretical interface between a first medium having a first predetermined refractive index and a second medium having a second predetermined refractive index. A band rejecting portion has a periodic refractive index profile whose periodicity and amplitude are selected to reflect a maximum amount of electromagnetic energy within the relfection band.

Abstract: Method of producing an enhanced output correlation signal from an image matching correlator includes the steps of further transforming data representing an input image to produce a transformed image, multiplying the transformed image by at least one reference filter function representing a reference image to be compared with the input image to produce a product signal, inverse fourier transforming the product signal to product the output correlation signal, and introducing phase distortions within the reference filter function, sufficient to greatly enhance peak values and narrow the area of the correlation peak of the output correlation signal. The method may utilize optical or digital electronic correlation and transformation.

Abstract: An optical processor includes a non-linear spatial light modulator defining an array of logic gates and having an output plane 10 ) and an input plane 12. The array is made up of a plurality of cells 14 each containing a plurality of logic gates 16. A lenslet array 18 comprising an array of lenslets 20 associated one with each cell 14 respectively focusses the oututs of the cells onto respective facets 22 of a holographic array 24. Each facet of the holographic array defines a predetermined mapping or routing configuration to map the respective cell onto the input plane 12. The cells may be mapped either precisely onto the predetermined cell of the input plane or in cell-shifted fashion. An optical processor is described which employs the arrangement illustrated in FIG. 1 to enable asembly of a plurality of similar interacting modules for implementing a regular algorithm such as a fast multiplier array.

Abstract: An optical device comprising a transparent plate having planar first reflecting surface and second reflecting surface, a reflector and a screen for forming interference fringes thereon. When a beam is incident on the transparent plate, a portion of the beam is reflected from the first reflecting surface, while the other portion of the beam enters the interior of the plate and is reflected at the second reflecting surface. The beam reflected from the first reflecting surface and further reflected from the reflector and the beam reflected at the second reflecting surface are superposed on the screen to produce interference fringes. The period of the interference fringes is easily variable by rotating the reflector and the screen around the line of their intersection.

Abstract: A method and improved apparatus for aligning a diffraction grating, as, for example, one used in tuning the output of a laser. The total angular misalignment .epsilon. between the incident and diffracted beams is a function of three angles: the tuning angle .theta.16, the angle of tilt .beta. between the plane of the grating 15 and the tuning rotational axis, and the angle .alpha. between the grating lines and the projection of the turning rotational axis in the plane of the grating 15. The present invention provides a method of aligning the diffraction grating so that the residual alignment error is very small over the desired range of tuning angle .theta. 16, by adjusting only .alpha. or only .beta. to zero at two reference tuning angles .theta..sub.0 and .theta..sub.1. Knowledge of the value of either .alpha. or .beta. is not necessary. For a CO.sub.2 laser tuned over the wavelength range 9.11 to 10.88 .mu.

Abstract: A diffractive lenslet array receives light from multiple lasers. The lenslet array is spaced apart from a partially reflecting mirror by a distance Z=nd.sup.2 /.lambda. where n is an integer or half integer, .lambda. is the laser wavelength and d is the spacing of the lenslets in the array. In a preferred embodiment the apparatus is a unitary design in which the lenslets are etched into one surface of a substrate and a parallel surface is coated to form the partially reflecting mirror. The lenslets abut one another to produce a fill factor (percentage of array containing light) close to one and each of the lenslets is a multistep diffractive lens. Diffractive speading over a round trip distance from lasers to mirror and back again causes feedback light from a single lenslet to couple into adjacent lenslets.

Abstract: An optical system for an in-line holographic lens or lens array which is designed to produce and pass a symmetrical focused beam of light while or blocking or attenuating the zero order in-line collimated beam illuminating and passed by the lens. Each holographic lens is designed to produce a symmetrical focused beam of light, and has particular applicability to high quality, low f-number holographic lenses. In the optical system, the in-line holographic lens is illuminated by a reconstruction beam of light such that it produces a focused beam of light along the optical axis of the lens, and also passes the zero order in-line reconstruction beam. A polarization rotator is positioned along the optical axis to receive the focused beam of light and also the zero order reconstruction beam, with the focused beam of light being incident thereon and traversing through the polarization rotator at different angles from the zero order reconstruction beam.

Abstract: The device provided makes it possible to see a collimated light image in relief. It is formed from a conventional collimator assembly comprising a convergent lens at the focal point of which the light representation to be collimated is placed. This light representation may be formed on the screen of a cathode ray tube. The screen is equipped with a micro-lens lattice. Each micro-lens is coupled to at least two adjacent pixels corresponding to the display of the same image point. A divergent optic is placed between the micro-lens lattice and the collimation optic so as to form with a convergent optic an assembly of the teleobjective type and to provide spatial separation of the collimated images and allow separate observation of a first image with the right eye and of second image with the left eye in the eye box.

Abstract: A system and method are described for achieving a high efficiency, full color display using color sensitive lenses such as holographic lenses. A lens assembly is composed of discrete lens elements (1, 2, 3) which are sensitive to different wavelengths bands of light. Each lens element (1, 2, 3) focuses input light within its waveband onto a corresponding target area, and generally transmits input light outside of its waveband. A separate target area (R, G, B) is provided for each lens element, whereby incoming light is divided into its constituent colors. The separate color stripes (R, G, B) may then be operated upon to produce a desired display. For incoming light which is to be divided into n different wavebands and directed onto separate target areas each having an area A, the area of each lens element is approximately nA, and each lens overlaps the next adjacent lens by an area approxmately equal to (n-1)A.

Abstract: The holographic diffraction efficiencies of photorefractive or electro-optic crystals, such as bismuth silicon oxide (BSO), increase while experiencing high AC voltages. The diffraction efficiency also increases with frequency of the AC voltages up to a saturation frequency. These enhancements are attributed to the response times of the crystal and the superposition of internal electric fields. The enhanced diffraction efficiency assists in retentively recording information bearing holograms in electro-optic crystalline media.