Abstract: An optical filter comprises a transparent and a filter layer. The filter layer contains a dye and a binder polymer. The dye is a cyanine dye represented by the formula (I). The filter layer further contains a specific metal complex. in which each of Z1 and Z2 independently is an non-metallic atomic group forming a five-membered or six-membered nitrogen-containing heterocyclic ring; each of R1 and R2 independently is an alkyl group, an alkenyl group, an aralkyl group or an aryl group; L1 is a methine chain consisting of an odd number of methines; X is an anion; and each of a, b and c independently is 0 or 1.

Abstract: An optical interference filter having high transmissivity at first and second passbands. The interference filter includes a first stack having a plurality of dielectric layers, a second stack having a plurality of dielectric layers, and a spacer interposed between the first and second stacks. Each of the dielectric layers included in the first and second stacks have optical thicknesses which vary quadratically. The dielectric layers have alternating high and low refractive indices.

Abstract: A wavelength division multiplexing device which can easily utilize existing optical fibers for increasing the transmission capacity by approximately several fold mainly in a short-range information communication network, comprising, as essential elements, a pair of 1×N optical couplers (2≦N≦16), N light emission devices in which one of peak wavelengths thereof differs from every other one by at least 30 nm and N light receivers having optical filters having light-transmission wavelength bands adjusted to correspond to said peak wavelengths, wherein the light emission devices and the light receivers having optical filters corresponding to peak wavelengths of the light emission devices form pairs, and said light emission devices of said light receivers are optically connected to N-port-side ports of one of the 1×N optical couplers.

Abstract: A multi-layered mirror has a substrate, a first layer of a first substance, a second layer of a second substance. The refractive index of the first substance in a utilized wavelength region is different from that of the second substance. The first and second layers are laminated alternately on the substrate. To obtain a high reflectivity and superior optical characteristics, a multi-layered structure is formed within either the first layer or the second layer using at least two substances whose real parts of the complex indices of refraction in the utilized wavelength region are approximately the same. Alternatively, a layer surface is smoothed before forming a next layer thereon. An exposure apparatus that uses multi-layered mirrors of the present invention uses light with higher efficiency.

Abstract: In a multilayer dielectric reflector, treating the surface of the reflector selectively increases the amount of light transmitted through the reflector. Various surface treatments can be used to permit light to transmit through the reflector that would otherwise be reflected by the reflector. In one such reflector, different portions of the surface have different coupling efficiencies for coupling light having a high propagation angle into the multilayer reflector. Those portions having higher coupling efficiencies on each side of the reflector have a higher degree of transmission.

Abstract: The present invention provides reflective films and other optical bodies which exhibit sharp bandedges on one or both sides of the main reflection bands. The optical bodies comprise multilayer stacks M.sub.1 and M.sub.2, each having first order reflections in a desired part of the spectrum and comprising optical repeating units R.sub.1 and R.sub.2, respectively. At least one of the optical repeating units R.sub.1 and R.sub.2 varies monotonically in optical thickness along the thickness of the associated multilayer stack.

Abstract: Stress compensating systems that reduces/compensates stress in a multilayer without loss in reflectivity, while reducing total film thickness compared to the earlier buffer-layer approach. The stress free multilayer systems contain multilayer systems with two different material combinations of opposite stress, where both systems give good reflectivity at the design wavelengths. The main advantage of the multilayer system design is that stress reduction does not require the deposition of any additional layers, as in the buffer layer approach. If the optical performance of the two systems at the design wavelength differ, the system with the poorer performance is deposited first, and then the system with better performance last, thus forming the top of the multilayer system.

Abstract: A filtering assembly includes a first substrate piece and a second substrate piece combined together with their dielectric band-pass filter-film adhered to each other in a face-to-face manner. A corresponding method for making the same includes following steps: (1) providing a raw substrate having at least a twice dimension of final assembly; (2) coating a designated dielectric band-pass filter-film on one side of said raw substrate; (3) dividing said coated substrate into two semi-finished substrate pieces with said filter-film thereon; (4) combining these two semi-finished substrate pieces together wherein said filter-film of one piece is directly adhered to that of another piece by a thin adhesive optical coupling layer, so that the filtering assembly has said filtering means sandwiched between said two substrates.

Abstract: A reflection control member includes a multilayer stack that is adhered to a substrate using a primer layer to promote adhesion. The multilayer stack includes pairs of layers in which the first layer is a grey metal and the second layer is a substantially transparent material. In the preferred embodiment, the grey metal is nickel chromium and the transparent layer is a silicon oxide. For each pair of layers, the grey metal is nearer to the surface of the substrate for which antireflection is a concern. The primer layer has a thickness of less than 50 angstroms. Although the primer layer is deposited in an essentially oxygen-free environment, it may oxidize following deposition.

Abstract: Negative group-delay-dispersion mirror (NGDD-mirror) multilayered structures are formed by two interferentially coupled Gires-Tournois interferometer cavities on a common, highly-reflective mirror in a single monolithic multilayered structure.

Abstract: The invention relates to a glazing pane having an "A" antireflection coating on at least one of its external faces, which antireflection coating comprises a stack of layers of materials having alternately high and low refractive indices. At least some of the layers of the said stack are pyrolysed layers, especially the final layer.

Abstract: An optical body comprising (a) a dielectric multilayer film having a reflecting band positioned to reflect infrared radiation of at least one polarization at an incident angle normal to the film, said reflecting band having a short wavelength bandedge .lambda..sub.a0 and long wavelength bandedge .lambda..sub.b0 at a normal incident angle, and a short wavelength bandedge .lambda..sub.a.theta. and long wavelength bandedge .lambda..sub.b.theta. at a maximum usage angle .theta., wherein .theta..sub.a.theta. is less than .lambda..sub.a0 and .lambda..sub.a0 is selectively positioned at a wavelength greater than about 700 nm; and (b) at least one component which at least partially absorbs or reflects radiation in the wavelength region between .lambda..sub.a.theta. and .lambda..sub.a0 at a normal angle of incidence.

Abstract: Tuned optical filters, filter systems, and methods for tuning filters make use of a tilted filter rotated about an oblique axis of a collimating lens or other structure. This rotation varies an angle of incidence of an optical signal directed at the filter at an oblique angle to the axis of rotation. Very fine adjustments of optical filters such as for tuning a first narrow band pass filter to match a center wavelength of another narrow band pass filter, can be provided with small angles between the axis of rotation and a normal to the filter surface, and also between the axis of rotation and the optical path for the incident light. Mechanical adjustment to the filtering frequency is facilitated by making use of a rotational motion about the axis of a GRIN collimating lens.

Abstract: A solar control film having low visible light transmittance and low visible light reflectance is comprised of a first sheet of transparent substrate material having deposited thereon a solar-load-reduction film for preferentially reducing infrared light energy transmitted through the film, and a second sheet of transparent substrate material having deposited thereon a thin, transparent film of metal effective to partially block light transmittance, wherein the first sheet of transparent substrate and the second sheet of transparent substrate are separated by an optically massive layer that prevents the constructive and destructive interference of reflected light. A preferred embodiment of a solar control film includes, in order, a pressure-sensitive adhesive layer, a polyethylene terephthalate layer, a Fabry-Perot interference filter layer, an adhesive layer, a grey metal layer, another polyethylene terephthalate layer, and a hardcoat layer.

Abstract: A reflective article has a multilayer film covering a patterned retroreflective layer. In one embodiment the patterned retroreflective layer includes a separate indicia layer covering a retroreflective substrate. The indicia are substantially hidden under normal viewing conditions but easily detectable under retroreflective lighting conditions. Various types of retroreflective layers are disclosed. The article can also include microstructured relief patterns which produce holographic images under ambient lighting but which disappear under retroreflective conditions. The multilayer film includes alternating layers of at least a first and second polymer, and has a relatively high reflectivity for normally incident light within a first spectral range which is approximately coextensive with the visible spectrum, and a relatively low reflectance for normally incident light within a second spectral range.

Abstract: The invention is directed to a system and method for extending the life of a bluish, greenish, or reddish colored gel, comprising a filter coating situated between a light source and a colored gel, which filter coating has a reflectance band falling in the same wavelength region of the visible light spectrum as the absorption band for the colored gel such that burning or bleaching of the color is prevented or delayed.

Abstract: A color filter plate includes a continuously-variable dichroic filter coating constituting a variable band-pass or variable band-reject filter having a spatially-modulated variable-density pattern formed in the coating, and provides continuously-variable hue and saturation characteristics along separate gradient axes. A color filter mechanism includes a sequential arrangement of rectangular or circular color filters, having continuously-variable band-pass or band-reject filter coatings, mounted in motorized carriages. One mechanism provides two-axis translation of the rectangular color filters while another mechanism provides translation and rotation of the circular color filters. A light projection system comprising a lamp with a reflector and a lens includes a color filter mechanism having sequential, continuously-variable band-pass and band-reject filters supported by motorized carriages mounted in a region where the beam diameter is small.

Abstract: A filter system for reflectively blocking laser radiation in the visible spectrum includes a multilayer interference structure arranged for reflectively blocking a continuous band of wavelengths including the laser radiation and transmitting other wavelengths in the visible spectrum. The filter system is arranged to control transmission of the other wavelengths of the visible spectrum such that the filter system has an essentially neutral transmission color and maximum photopic transmission consistent with the band of wavelengths reflectively blocked.

Abstract: An endoscope optical system is used in an endoscope which can be combined with at least two laser treatment units that produce different wavelengths. At least two filters for removing laser light are provided in the path of the optical system, and are arranged at positions where angles of incidence or emergence of a chief ray are different. In this way, even with the laser treatment units using a plurality of wavelengths, laser light of the plurality of wavelengths can be removed.

Abstract: A process suitable for forming multi-layer (up to at least several hundred layers) monotonic/linear variable/wedge filter coatings on a single substrate surface and for forming monolithic filter assemblies which incorporate such filters, is disclosed along with the designs for such filters. The monolithic process uses radially variable filter fabrication techniques in combination with ion-assisted deposition to form stress controlled, radially variable filter coatings of the desired varied optical profile, preferably using high and low index materials stich as tantala and silica. Stress is minimized by balancing the amount of ion assist and the coating rate. Slices are cut radially from the substrate to form quasi-linear variable filters. Other coatings such as, but not limited to, a wide band hot mirror can be formed on the opposite surface of the substrate from the radially variable LVF method.

Abstract: A high reflectivity, broad band mirror for a high flux laser and a process for producing such a mirror. The mirror includes a substrate on which is formed a metallic layer such as aluminum. A stack of layers are formed on the metallic layer. The stack includes alternating layers of two materials with the refractive index of one material being higher than that of the other. A surface layer of a third material is placed on the stack. The surface layer has a refractive index which varies in accordance with the continuous periodic profile. The mirror is formed by depositing the metallic layer on a substrate and forming the stack by an ion beam sputtering method.

Abstract: An optical filter includes a dielectric layer formed within a resonant optical cavity, with the dielectric layer having formed therein a sub-wavelength periodic structure to define, at least in part, a wavelength for transmission of light through the resonant optical cavity. The sub-wavelength periodic structure can be formed either by removing material from the dielectric layer (e.g. by etching through an electron-beam defined mask), or by altering the composition of the layer (e.g. by ion implantation). Different portions of the dielectric layer can be patterned to form one or more optical interference filter elements having different light transmission wavelengths so that the optical filter can filter incident light according to wavelength and/or polarization. For some embodiments, the optical filter can include a detector element in optical alignment with each optical interference filter element to quantify or measure the filtered light for analysis thereof.

Abstract: A reflecting fluorescence microscope includes an excitation filter for converting a beam of light projected from a reflecting illumination light source into light having a plurality of wavelength regions of narrow-band excitation light, a dichroic mirror for irradiating a specimen with the light having a plurality of wavelength regions of narrow-band excitation light converted by the excitation filter to transmit various kinds of fluorescent light emitted from the specimen, and an absorption filter for absorbing an unwanted wavelength region from the light transmitted through the dichroic mirror to transmit the wavelength of a fluorescent image. In this reflecting fluorescence microscope, at least one band-stop filter having at least one absorption band is disposed in a reflecting illumination optical path before the dichroic mirror so as to absorb the wavelengths of a transmission band and change the amount of the light having a plurality of wavelength regions of narrow-band excitation light.

Abstract: A filter system to transmit short wavelength radiation and reflect long wavelength radiation for a thermophotovoltaic energy conversion cell comprises an optically transparent substrate segregation layer with at least one coherent wavelength in optical thickness; a dielectric interference filter deposited on one side of the substrate segregation layer, the interference filter being disposed toward the source of radiation, the interference filter including a plurality of alternating layers of high and low optical index materials adapted to change from transmitting to reflecting at a nominal wavelength .lambda..sub.IF approximately equal to the bandgap wavelength .lambda..sub.g of the thermophotovoltaic cell, the interference filter being adapted to transmit incident radiation from about 0.5.lambda..sub.IF to .lambda..sub.IF and reflect from .lambda..sub.IF to about 2.lambda..sub.

Abstract: An optical filter is formed from at least two gratings (102,103) located in a waveguide region (104) of a` semiconductor optical device (101). Each grating has a multiple peak optical passband. The gratings are spaced apart in the waveguide region and form an optical cavity having a comb-filter characteristic. The gratings may be located in the active region of an optical gain element and in a preferred example are superstructure gratings (SSGs). A number of filters may be joined together in series.

Abstract: A sunglass has a multilayer coating on its concave (rear) surface that comprises a absorbing layer and at least one composite layer for reducing transmittance of UV radiation. Reflection of visible light at the concave surface is minimized.

Abstract: An improved system is provided suitable for use in landing an aircraft (for example, helicopter, RPV, VTOL) on shipboard comprising a support, base, platform or housing, reciprocal from remote a landing area on the deck of a ship to a position proximate the landing area, the housing carrying an upwardly directed light sensor comprising a lens system and a pair of band-pass filters, one filter before the lens system of the sensor and one after the lens system, the filters each passing the identical wavelength of light at its center but which each need not have the same band width as the other, a pulse detector in close proximity to the upwardly directed light sensor, and means for securing the aircraft to the support, housing, base or platform.

Abstract: A multilayered reflective body which is thermoformable and capable of being fabricated into a number of parts while maintaining a uniform reflective appearance is provided. The reflective polymeric body is formed from at least two diverse polymeric materials which differ in refractive index and which are arranged in substantially parallel alternating layers. The polymeric body is reflective in appearance yet is transparent or, colored if a coloring agent is included, upon illumination from a back light source. The polymeric body has application in variety of areas such as in an automobile lighting lens which is reflective and thereby indiscernible yet transmissive upon exposure to a back light source. Additionally, various parts of consumer appliances, for example a refrigerator door, can be formed from the polymeric body.

Abstract: A color filter system for an optical system, applicable to optical systems in color image scanners, copiers, video cameras and digital cameras. The optical system includes a photosensor army, transmissive color filters on the photosensor array and a corrective reflective filter adjacent to the photosensor array. The transmissive color filters on the photosensor array are imperfect, transmitting too much visible red as well as infrared. The adjacent reflective filter compensates by suppressing longer visible red wavelengths and infrared wavelengths. The combination provides color precision with cost and manufacturing advantages relative to attempting to provide precise transmissive filters on the photosensor array or relative to providing compensation filters elsewhere in the system.

Abstract: The present invention is directed to an antireflection film having a multilayer structure in which an antireflection multi-layer film including at least two thin films is formed on a substrate, wherein at least one of the thin films contains a coloring agent. The antireflection multi-layer film absorbs light of an entire range of wavelength of 400-700 nm, and the reflectance of the antireflection multi-layer film with regard to the wavelength, light of which this antireflection multi-layer film can absorb, is smaller than the reflectance of the substrate. The antireflection film can be applied to a cathode ray tube or a light-transmitting display substrate of a display apparatus such as a liquid crystal display apparatus for the purpose of effectively avoiding reflection of external light.

Abstract: An optical filter for providing an enhanced image. The filter may comprise at least one substrate, layers of a low refractive index material and layers of a high refractive index material. The layers are stacked so that the filter blocks passbands at 490 nm and 590 nm as well as other image-confusing radiation. Light which is transmitted by the filter provides an enhanced image for viewing by the human eye as well as nonhuman detectors.

Abstract: An arrangement is produced for protection against harmful effects of radiation and for indicating such radiation which can preferably be designed as a viewing window or as goggles and can be used for protecting the eyes from injury due to high-intensity electromagnetic radiation. It includes a transparent substrate and a sequence of thin optical layers which are applied to this substrate and are arranged according to the principle of an optical thin-film resonance absorber system.

Abstract: A polarization separation mirror is made by evaporation-depositing a first multi-layers thin film and a second multi-layers thin film respectively on both surfaces of a transparent substrate, the mirror acts as a polarization beam splitter by cementing it between two transparent prism bodies. By shifting the relative film thicknesses of the first multi-layers thin film and of the second multi-layers thin film, reflecting wavelength range for the S-polarization component is changed.

Abstract: An optical filter is provided for suppressing unwanted reflections of background light when used with a display device such as a cathode ray tube or an electroluminescent screen, or in optical communication or surveillance. The filter has multiple thin layers including a first series of layers for suppressing reflections from its outer surface and a second series of layers constituting a bandpass interference filter. The first series of layers is arranged to suppress reflections over a broad wavelength band while the second series of layers allows transmittance over a relatively narrow wavelength passband within the broad wavelength band, resulting in improved contrast when the display is used in situations of high background light.

Abstract: A welding helmet including an optical protective lens including one or more liquid crystal cells as a variable optical transmission device responsive to a prescribed input to vary light transmission and light blocking characteristics thereof, and a hot mirror band pass filter having a relatively wide transmission characteristic in the visible spectrum and filtering characteristics in the infrared spectrum, the variable optical transmission device being tuned to provide a warning to indicate a nonoperating condition; and the variable optical transmission device being operative in a drive to dark mode for fast operation. Also disclosed is a method for protecting the eyes of a welder while providing a bright clear state, a fast switching to dark state, and the providing of an indication of a power off or failure state.

Abstract: A color image reading apparatus includes a multiple-line sensor in which a plurality of one-dimensional sensor arrays are arranged on a single substrate, a projection optical system for projecting a subject on the sensor, and a color separator disposed in an optical path between the projection optical system and the sensor, for color-separating light from the subject into a plurality of color beams. The color separator includes a volume hologram and an optical interference film.

Abstract: An optical filter (18) includes a first layer (22) of material having a bandgap and being doped with an impurity having an energy level in the bandgap such that the first layer absorbs optical energy below a first wavelength and transmits optical energy thereabove. The filter further includes a second layer of optical material (26) disposed on said first layer (22) which transmits optical energy at a second wavelength, above the first wavelength, and reflects optical energy at a third wavelength above the second wavelength. The first and second layers in combination provide a filter (18) with high transmission in-band, low transmission out-of-band and a sharp cutoff therebetween.

Abstract: A diffraction grating unit includes a reflection type diffraction grating; a transparent medium; and a filter which is formed on the diffraction grating through the transparent medium so as to be disposed on an incident surface of the diffraction grating unit; wherein the filter transmits therethrough a ray having a specific wavelength but reflects a further ray having a wavelength equal to a half of the specific wavelength of the ray, and a second-harmonic generator employing the diffraction grating unit.

Abstract: The present invention is directed to an antireflection film having a multilayer structure in which an antireflection multilayer film including at least two thin films is formed on a substrate, wherein at least one of the thin films contains a coloring agent. The antireflection multi-layer film absorbs light of an entire range of wavelength of 400-700 nm, and the reflectance of the antireflection multi-layer film with regard to the wavelength, light of which this antireflection multi-layer film can absorb, is smaller than the reflectance of the substrate. The antireflection film can be applied to a cathode ray tube or a light-transmitting display substrate of a display apparatus such as a liquid crystal display apparatus for the purpose of effectively avoiding reflection of external light.

Abstract: A two-metal grating is produced by vacuum depositing a first dielectric cing upon a separation layer formed upon a mandrel; then depositing a first optically opaque metallic layer, etching the layer to form stripes; then vacuum depositing a second optically opaque film; then electroforming a backing structure and separating the dielectric coating from the separation layer on the mandrel to form a free-standing grating structure having a smooth surface. This structure can then be affixed to a metallic mirror. A buried phase grating can also be fabricated by additionally depositing a second dielectric layer and a third metallic layer.

Abstract: A dichroic optical filter including a substrate that is substantially transparent to visible radiation, and an oxide semiconductor layer on the substrate for reflecting an infrared wavelength (such as an infrared treatment beam wavelength). An example of a suitable oxide semiconductor for reflecting a treatment beam from a CO.sub.2 layer is indium tin oxide. Preferably, the filter includes a specially designed multilayer coating on the oxide semiconductor layer to enhance the reflection of infrared and longer wavelength radiation. This multilayer coating includes alternating quarter-wave layers of high and low refractive index materials, each having an optical thickness substantially equal to a quarter-wavelength of infrared radiation to be reflected.

Abstract: A display especially for viewing by a night-vision aid has an array of LED's which emit green light. A dichroic filter is located in front of the display and transmits radiation at the peak emission of the diodes but reflects radiation in the range to which the night-vision aid is sensitive. A bandpass filter located in front of the dichroic filter prevents transmission of longer wavelengths, and a circularly polarizing filter in front of the bandpass filter prevents transmission of radiation reflected specularly from surfaces behind it.

Abstract: Color transparencies having more than one imaged dichroic filter, and an imaged neutral density filter, layered on one side of a single glass substrate, and processes for making the same, are disclosed. In one embodiment, the color transparency is produced by a deposition process including the steps of coating a glass substrate with a photoresist and developing an image thereupon, depositing alternating layers of high and low refractive index dielectrics to form a dichroic layer of a primary subtractive color, stripping the photoresist from the glass, preparing at least one additional imaged dichroic filter on the first, and preparing a neutral density filter on the substrate on the side having the layered dichroic filters. A red antihalation coating may be applied to the lower surface of the glass substrate prior to exposing the photoresist to prevent undesirable exposure of additional portions of the photoresist layer.

Abstract: A coating, composed of an optically effective layer system for substrates, whereby the layer system has a high antireflective effect. On a front side of the substrate, facing the observer, in sequence from the front side to the observer, a first layer is arranged on the substrate, functioning as dielectric and comprising metal oxide. Thereupon follows a second layer comprising nitride, preferably TiN.sub.x (x is equal to or greater than 1, preferably x=1.05). A third layer follows functioning as dielectric and comprising metal oxide. Thereupon a fourth layer follows comprising nitride, preferably TiN.sub.x (x is equal to or greater than 1, preferably x=1.05). A fifth layer follows functioning as dielectric comprising metal oxide. On a backside of the substrate a TiN.sub.x -layer (x.gtoreq.1, preferably x=1.05) is arranged.

Abstract: A light sensor comprises optical filters, an interference filter and a photoelectric converting element which receives and photoelectrically converts light which has passed through the optical filters and the interference filter. An incident angle of the incident light on the interference filter can be changed so as to realize a desirable spectral sensitivity in a combination of the optical filters, the interference filter and the photoelectric converting element. The incident angle can be changed by a mounting structure that can rotate about an optical axis.

Abstract: A ghost image eliminating optical system in a transmission optical system including a plurality of transmission optical elements having boundary reflection surfaces, so that a ghost image can be formed by light reflected by at least two specific boundary reflection surfaces, wherein the specific boundary reflection surfaces are coated with at least two anti-reflection coatings having complementary reflection characteristics to eliminate the ghost image.

Abstract: An optical thin film filter for the spatial and spectral separation of two or more transmitting bands of radiant energy. For a two band filter the filter has a substrate substantially transparent to radiant energy in the transmitted bands. On one surface of said substrate is a multilayer interference coating that transmits both wavelength bands of interest. On the other surface of said substrate (or on the same surface) are two sets of non-overlapping butted, parallel stripes with one set being alternately interspersed with the other. The widths of said stripes are varied to provide for precisely defined regions of spatial and spectral delineation. One set of stripes is capable of transmitting one of the bands of interest and reflecting all others, while the second set of stripes is capable of transmitting at least one band different from the one band transmitted by said first set of stripes and reflecting all others.

Abstract: A measuring instrument that must transmit predetermined wavelengths of optical radiation has an optical filter assembly that can be conveniently manufactured. The optical filter assembly can be coated to provide optical coatings on either side of the substrate, and a masking layer can be deposited to encompass the peripheral edges of the optical coatings and exposed portions of the substrate to eliminate the problem of optical noise resulting from optical radiation contact with the edges of the coating layers.

Abstract: A color display device has groups of liquid crystal display elements controlled by respective TFTs, the groups providing respective different color outputs, e.g. red, green and blue, and being either interspersed in a single panel with individual elements associated with color filter elements or in respective separate panels illuminated by differently colored light. The TFTs are of multilayer structure having semiconductor, gate insulator and gate layers. At least one layer thickness of the TFTs is different from group to group and is selected in accordance with the color light to which they are subjected so as to reduce absorption of that light, and consequently photo-induced currents in their semiconductor layers. Significantly reduced absorption is achievable by appropriate choice for example of semiconductor and insulator layer thicknesses based on optical interference considerations. The device can be used as a projection display device.

Abstract: An improved system is provided suitable for use in landing an aircraft (for example, helicopter, RPV, VTOL) on shipboard comprising a support, base, platform or housing, reciprocal from remote a landing area on the deck of a ship to a position proximate the landing area, the housing carrying an upwardly directed light sensor comprising a lens system and a pair of band-pass filters, one filter before the lens system of the sensor and one after the lens system, the filters each passing the identical wavelength of light at its center but which each need not have the same band width as the other, a pulse detector in close proximity to the upwardly directed light sensor, and means for securing the aircraft to the support, housing, base or platform.