Abstract: A multi-faceted mirror forms a retroreflector for a resonator loop in a free electron laser (FEL) operating in the XUV (.lambda.=10-100 nm). The number of facets is determined by the angle-of-incidence needed to obtain total external reflectance (TER) from the facet surface and the angle through which the FEL beam is to be turned. Angles-of-incidence greater than the angle for TER may be used to increase the area of the beam incident on the surface and reduce energy absorption density. Suitable surface films having TER in the 10-100 nm range may be formed from a variety of materials, including Al, single-crystal Si, Ag, and Rh. One of the facets is formed as an off-axis conic section to collimate the output beam with minimum astigmatism.

Abstract: An achromatic infrared retarder is described which comprises a substrate supporting an optically reflective surface, two identical prisms of preselected optical material disposed in confronting relationship with the reflecting surface therebetween and defining an optical axis through the prisms along which a light beam is selectably directable, each prism having a first optical surface orientable perpendicular to the optical axis, a second optical surface disposed at a preselected angle to the first surface, and a third optical surface disposed at the preselected angle to the second surface, the angle preselected in size corresponding to the material comprising the prisms in order to provide total internal reflection of a light beam directed along the axis at the second surface, the prisms being disposed so as to define a region bounded by respective third optical surfaces of the prisms and the reflective surface therebetween.

Abstract: An optical resonator for stabilizing a laser source is useful for homodyne and heterodyne applications. The structural resonator length is considerably reduced by placing a laser source, such as a semiconductor laser (10) in an opening of an optical grating, whereby the laser beam is directed onto a parabolic mirror (15), which reflects the laser beam onto the grating (11). Thus, a "folded" beam path results.

Abstract: A programmable frequency identifier circuit for identifying the frequency of a contaminated signal including a digital finite impulse response filter, a zero crossing detector, a zero crossing counter, and a frequency range decoder. The filter is a programmable filter for filtering signals of the form: S(n)=S.sub.1 (n)+S.sub.2 (n)=A cos 2.pi.F.sub.1 (n)+B cos 2.pi.F.sub.2 (n) where S.sub.1 (n)=desired signal, S.sub.2 (n)=contamination, F.sub.1 =passband frequency, F.sub.2 =stopband frequency, and A,B=constants. The zero-crossing counter counts the sign changes occuring during a programmably determined frame time. The number of zero crossings occuring during the frame time is a number representing the desired frequency. The frequency range decoder is programmed with a plurality of frequency range boundaries similarly represented by a count that is based upon the programmable frame time.

Abstract: An optical correlator system comprising a laser to generate a signal beam, a film to spatially modulate that beam, and a beam splitter to split the signal beam into two component beams. The first component beam is directed onto a first side of a multiple holographic lens, which generates from the component beam a first matrix of individually converging beams and a second matrix of individually diverging beams. The second component beam is directed onto a second side of the holographic lens, which generates from this component beam a third matrix of individually converging beams and a fourth matrix of individually diverging beams. The beams of the first and third matrices are focused by the holographic lens onto first and second matched filters, respectively, and correcting optical elements are used to focus the beams of the second and fourth matrices onto third and fourth matched filters, respectively.

Abstract: A contact lens of soft, pliable opthalmic plastic material, said lens when in its dehydrated state having a spherical back surface which in its hydrated state conforms to the corneal curvature of the wearer's eye and, when in its dehydrated state, having an aspheric front surface which is a surface of revolution of polar coordinate form, having an asphericity which is a function of (n)[f]<sin(a)> where (a) is the polar angle, and (n) is a radial offset of a tool-controlling circular surface.

Abstract: Gradient optical density transmissive light directing devices (24, 26, 28, 30) and fabrication thereof are disclosed herein. Example of such devices include concentrators, lenses and compound lenses. The present invention teaches a process for the fabrication of glass light transmitting devices having a chosen gradient in index of refraction either bidirectionally (radially and longitudinally relative to an optical axis) or in three dimensions. The present invention further describes the design of several interesting optical devices by particular choices of the gradient in the index of refraction thereof. Such articles have numerous uses in the optics, optical fiber and solar technology industries for the purposes of designing compound lens systems using a single, integral lens, coupling light into fibers and for concentrating and directing light from a source having a significant angular variation to an energy collecting and/or conversion devices such as a photovoltaic cell, to name but a few applications.

Abstract: An objective of variable focal length includes a plurality of lens units of which the first, counting from front, is of negative power and the second is of positive power. At least the first and second lens units are moved with variation of the air separation therebetween to vary the focal length of the entire system. The objective is characterized in that at least one of the lens units is included with at least one refractive index distribution type lens arranged on the common optical axis of the other lenses.

Abstract: A spectacle lens for half-eye spectacles is described which in accordance with the present invention has at least one aspherical surface whose surface focal power increased progressively from the upper rim area of the spectacle lens towards the lens bottom.In a preferred version example, the spectacle lens has a prismatic power of zero in the upper rim area.In a further preferred version example, the power of the spectacle lens increases progressively from a value other than zero in the upper rim towards the lens bottom.

Abstract: The invention features an optical spread spectrum decoder wherein linear, non-linear, and discontinuous broadband RF signals can be optically decoded.The system introduces a weighting function into a local oscillator beam, which is then combined with a laser beam which has been modulated with the RF signal, processed to remove unwanted spectral components and then compressed. The combined beams are then down-converted to recover the RF signal.

Abstract: The invention is a method of making a cosmetic contact lens that changes the apparent color of the eye. This is accomplished by dying the iris area of the convex lens surface the desired transparent color. The convex surface is expanded by a swelling agent. The swelling agent increases the pore size allowing the precipitating solution to move deeper into the convex lens surface below the dyed surface layer. The precipitating solution is reacted to form an insoluble light reflecting layer. When the lens is placed on the eye, the opaque light reflecting layer is viewed through the transparent dyed surface layer changing the apparent color of the eye.

Abstract: A method and apparatus are disclosed for correcting complex phase aberrations in a thick window in an airborne vehicle using the technique of phase conjunction. A conjugate element of the window is fabricated by machining. The conjugate element and an imaging lens are positioned behind the window such that the window is imaged onto the conjugate element. Phase aberrations produced when broadband radiation is passed through the window are removed when the wavefront passes through the imaging lens and conjugate element. In another embodiment, halogram is prepared of the wavefront passing through the window. The spatial phase information encoded in the hologram is read out by a phase measurement system and then fed into a computer where the conjugate wavefront is calculated. The conjugate wavefront is then written into a thin corrector plate of refractive material. The corrector plate with the conjugate wavefront imprinted thereon is then placed at the location where the hologram was initially formed.

Abstract: A low emissivity, low shading coefficient, low reflectance window consisting of two panes of glass. The first pane having a low wave infrared reflecting and a visible light and short wave infrared absorbing section of coatings on its inside surface. A second pane spaced about one half inch from the inside surface of the first pane to protect the coatings on the first pane and to insulate the room form the heat generated on the light and heat absorbing coating of the first pane. The infrared reflecting section consisting of four layers of metals and metal oxides. The first layer of metal oxides selected from the group consisting of tin oxide, zinc oxide and a combination of zinc and tin oxide. The second layer is silver. The third layer consisting of a metal selected from the group consisting of aluminum, titanium, zinc and tin. The fourth layer selected from the same group as the first layer. The visible light and short wave infrared absorbing section consists of a coating of titanium nitride.

Abstract: This invention consists of a Fresnel lens having focusing grooves on both sides of a single element. The relative frequencies of the grooved surfaces are controlled such that Moire fringe patterns between the two grooved surfaces are reduced. Specifically, the frequency of the Fresnel elements on one surface of the element is at least four times that of the Fresnel elements on the other surface and not a integral multiple thereof.

Abstract: The occurrence and frequency of a periodic component embedded in a composite waveform including noise is detected by real time calculating the autocorrelation function of the waveform and deducing the frequency of the periodic component from the value of the autocorrelation function coefficients. An analog-to-digital converter periodically transforms the waveform into samples having q bits. The samples are delayed by a predetermined time interval .DELTA.t and multiples thereof, to derive 2n delayed samples, x.sub.i, x.sub.i-1 . . . x.sub.i-2n. The delayed samples are multipled to derive 2n products, such that the first n products are represented by x.sub.1 .multidot.x.sub.i-k and the second n products are represented by x.sub.1-n .multidot.x.sub.i-(n+k), where k is selectively 1 . . . n. Difference between the first and second products are obtained as (P.sub.1 -P.sub.n+1) . . . (P.sub.n-1 -P.sub.2n), where P.sub.1 =x.sub.i .multidot.x.sub.i-1, P.sub.n-1 =x.sub.i .multidot.x.sub.i-n, P.sub.+1 =x.sub.i-n .

Abstract: An improved opthalmic lens is disclosed which has a plurality of alternating power zones with a continously varying power within each zone, as well as in transition from one zone to another. In other words, a plurality of concentric zones (at least two) are provided in which the variation from far to near vision correction is continuous, i.e., from near correction focal power to far correction focal power, then back to near, and again back to far, or vice versa. This change is continuous (progressive), without any abrupt correction changes, or "edges".Two versions of the invention are disclosed. In the first version continuous, alternating power variation is accomplished by a continuously changing curvature of the lens posterior surface, thereby altering the angle of impact of light rays on the eye.

Abstract: An encapsulated-lens retroreflective sheeting comprising a monolayer of lenses partially embedded in a binder layer, a specularly reflective layer underlying the lenses, and a cover film sealed to the binder layer along a network of interconnecting lines forming hermetically sealed cells within which the lenses are encapsulated and have an air interface, wherein the cover film comprises polyethylene, or polypropylene, or a copolymer comprising a major portion by weight of at least one of ethylene or propylene and a minor portion by weight of a comonomer. Such a cover film affords high flexibility, improved impact resistance, resistance to moisture absorption, and greater toughness to the retroreflective sheeting. In some embodiments the cover film is multi-layer.

Abstract: A short-wave-pass optical filter, including a partially absorbing or transparent substrate coated by a set of layers having different quarter-wave optical thicknesses, which is designed to reflect visible radiation of a selected color white transmitting visible radiation and maintaining a neutral color balance. The inventive filter is designed so that the desired reflected color (and the transmitted neutral color balance) is substantially independent of viewing angle (i.e., the incidence angle). In a preferred embodiment, the substrate is composed of UV-absorbing glass, and the coating is substantially a double quarter-wave stack of alternating layers of SiO.sub.2 and TiO.sub.2, TiO or Ti.sub.2 O.sub.3. The reflectance of the inventive filter (as a function of wavelength) is designed to have a ripple in at least one segment of the visible spectrum, but to have no significant ripples in all other segments of the visible spectrum.

Abstract: A method of preparing a reflection hologram which includes mounting a transmission hologram in register with a portion of transparent photosensitive holographic material there being present there between a filter to cut out zero order light transmitted through the transmission hologram, there being present on each side of an assembly which includes the hologram and the holographic material a light reflecting surface then causing a beam of light from a laser source to pass through a holographic optical element (H.O.E.

Abstract: An information storage system records on a medium with a magneto-optical storage layer and a ferrimagnetic control layer. A higher power write beam is used to impose an upward magnetic orientation and a lower power write beam is used to impose a downward magnetic orientation in the domain. The control layer has an initial downward magnetic orientation, the magnetization of regions of the control layer can be inverted to an upward orientation temporarily while the region is heated above a compensation temperature. The magnetization of the region is restored to its initial downward orientation upon restoration of ambient temperature since neither the higher power nor the lower power write beam heats the control layer to its Curie temperature. The distributed optical and thermal properties of the medium are selected so that, upon heating of the medium by dissipated laser energy, the peak temperature of the control layer occurs after the peak temperature for the storage layer.