Abstract: An electrically adjustable phase-shifting device is arranged on a substrate comprising at least a first waveguide designed for guiding optical signals and a thermoelectric element arranged adjacent to the first waveguide in order to shift the phase of an optical signal in the first waveguide by means of a thermo-optic effect according to a control voltage applied to the thermoelectric element. In one embodiment, the thermoelectric element is a Peitier element which comprises at least first and second electrically conducting segments which are serially connected, the first and second elements alternating consecutively.

Abstract: A light emission microscope includes a low temperature detector array which receives light through a room temperature projection optics system from a device under test. A cold aperture including a movable cold stop and a cryogenic filter absorbs unwanted thermal radiation emitted by the optics system. In one embodiment, a high resolution CCD camera can be used with the low temperature detector array and camera with a computer-controlled mirror providing emitted light to both cameras.

Abstract: The present invention provides an imaging assembly comprising: (a) a modulator crystal comprising a first surface and a second surface substantially opposite to the first surface, wherein the first surface comprises an active area; and (b) a heating element for heating the modulator crystal to a temperature within a predetermined temperature range, wherein the heating element is positioned under the modulator crystal and comprises a first surface, wherein the heating element first surface faces the modulator crystal second surface and covers a portion of the modulator crystal second surface such that the active area of the first surface of the modulator crystal has a homogeneous temperature.

Abstract: A MEMS optical display system includes an illumination source for providing illumination light, a collimating lens for receiving the illumination light and forming from it collimated illumination light, and a converging microlens array having an array of lenslets that converge the collimated illumination light. The converging microlens array directs the illumination light to a microelectrical mechanical system (MEMS) optical modulator. The MEMS optical modulator includes, for example, a planar substrate through which multiple pixel apertures extend and multiple MEMS actuators that support and selectively position MEMS shutters over the apertures. A MEMS actuator and MEMS shutter, together with a corresponding aperture, correspond to pixel. The light from the converging microlens array is focused through the apertures and is selectively modulated according to the positioning of the MEMS shutters by the MEMS actuators, thereby to impart image information on the illumination light.

Abstract: Reconfigurable radiant energy reflectors (3) of very low areal densities are formed of a laminate of a thin layer of a shape memory alloy (17) and a thin film or membrane material (15). The outer surface of the membrane provides the energy reflecting surface (16) and a support member (11) is attached to the laminate for application in a system. In a preferred embodiment, the shape memory alloy (17) is compositionally graded (18, 19, 29, 21) and exhibits a two-way shape memory effect and a heater (5) serves as the actuator to the reflector.

Abstract: A multi-channel acousto-optic modulator contains an integrated structure for providing active compensation for transient thermal effects. A plurality of electro-thermal elements in the form of resistive strips are interleaved with acoustic wave launching transducers, to which signals are applied for modulating respective acoustic waves launched into an acousto-optic medium. The resistive strips receive electrical signals that controllably introduce respective thermal energy components into the acousto-optic medium adjacent to the signal launch transducers, in a manner that causes the overall spatial distribution of thermal energy in the acousto-optic medium to have a prescribed characteristic. By establishing an thermal gradient characteristic across all the channels of the RF signal processor, and compensating each channel on an individual basis, the invention effectively compensates for time-dependent variations in heating, resulting in a substantially level thermal behavior.

Abstract: A nonlinear optical crystal device, a wavelength conversion element, is surrounded with a heat sink having cooling fins. Cartridge heaters for uniformly heating the nonlinear optical crystal device are arranged in the heat sink, and the temperature of the cartridge heater is regulated by a heater controller. Laser light is input into the nonlinear optical crystal device, and delivered therefrom after its wavelength is converted into a shortened wavelength. When the repetition frequency of laser light is high, heating by the heaters is stopped, and cooling is effected with the heat sink. When the repetition frequency of laser light is low, heating by the heaters is carried out to maintain the temperature of the nonlinear optical crystal device to be a temperature at which a conversion efficiency is satisfactory.

Abstract: Reconfigurable radiant energy reflectors (3) of very low areal densities are formed of a laminate of a thin layer of a shape memory alloy (17) and a thin film or membrane material (15). The outer surface of the membrane provides the energy reflecting surface (16) and a support member (11) is attached to the laminate for application in a system. In a preferred embodiment, the shape memory alloy (17) is compositionally graded (18, 19, 29, 21) and exhibits a two-way shape memory effect and a heater (5) serves as the actuator to the reflector.

Abstract: A modulator for modulating an incident beam of light, includes a structure defining a cavity and having a base and side walls surrounding the base; a first plurality of equally spaced apart thermally deformable reflective members having opposing end edges integrally formed in the side walls of the structure above the cavity.

Abstract: A method and apparatus for controlling a charge/discharge voltage applied to an EC device to ensure that an appropriate voltage drop across the EC device is maintained during charge and/or discharge modes of operation. The appropriate voltage drop is determined with respect to a temperature measurement proximate the EC device. The charge level of the device is monitored using a coulomb counter circuit having a topology designed to minimize interference in the operation of the EC device.

Abstract: A thermo-optic lens of the present invention includes a plurality of parallel heating elements having substantially constant center-to-center spacing and respective dimensions varying from the outermost heating elements to the innermost heating elements, and at least two conductive elements for providing a potential across the heating elements. The dimensions of the heating elements are varied such that a parabolic temperature distribution is generated within the thermo-optic lens.

Abstract: The device of the present invention includes an electrochromic element having a transmittance that varies in response to an electrical signal, a base substrate disposed in spaced relation to the electrochromic element, a seal disposed between the base substrate and the electrochromic element, and an optical sensor. The seal, base substrate, and electrochromic element form a sealed cavity therebetween, in which the optical sensor is disposed. According to another embodiment, an electrochromic device is provided that includes a first substrate, an electrochromic medium disposed on the first substrate, a pair of electrodes in contact with the electrochromic medium, a pair of conductive clips, each in electrical contact with a respective one of the electrodes, and two pairs of electrical lead posts for mounting the first substrate to the circuit board. Each pair of lead posts is attached to, and extends from, a respective one of the conductive clips.

Abstract: A method and apparatus for controlling a charge/discharge voltage applied to an EC device to ensure that an appropriate voltage drop across the EC device is maintained during charge and/or discharge modes of operation. The appropriate voltage drop is determined with respect to a temperature measurement proximate the EC device. The charge level of the device is monitored using a coulomb counter circuit having a topology designed to minimize interference in the operation of the EC device.

Abstract: A thermal actuator includes a first arm having a proximal end and a distal end, a second arm, parallel to the first arm, having a proximal end and a distal end, and a third arm arranged between and parallel to the first and second arms, the third arm having a proximal end and a distal end. The third arm has at least one portion at the distal end of the third arm having a width that is substantially larger than a width of the first arm and a width of the second arm. The distal ends of the first, second and third arms are coupled together to form a distal end of the thermal actuator, and the first, second and third arms preferably are made of a single material. A number of thermal actuators can be arranged in an array. The thermal actuator or array of thermal actuators can be coupled to an applicator.

Abstract: An apparatus and associated method for altering the propagation constant of a region of deflecting propagation constant in an optical waveguide. The method comprising positioning an electrode of an electrode shape proximate the waveguide. A region of deflecting propagation constant is projected into the waveguide and corresponds, in shape, to the electrode shape by applying a voltage to the shaped electrode. The propagation constant of the region of deflecting propagation constant is controlled by varying the voltage that adjusts a deflection angle applied to an input optical signal flowing through the waveguide.

Abstract: A system (SYS) for optically transmitting information, e.g., television signals, from a subcenter (HUB), e.g., a cable television head end, over a passive optical distribution network to a plurality of optical network units (ONU) includes a plurality of nodes (K1, . . . , Km) for optically transmitting further information, e.g., telephone signals, and a plurality of optical couplers (C1, C2). The further information of each node (K1, . . . , Km) is fed via a respective coupler (C1, C2) into a transmission line connected to only part of the plurality of optical network units (ONU), e.g., to only one optical network unit (ONU). Each optical network unit (ONU) is connected to a group of customer locations (END) and, for the transmission of information from this group of customer locations (END), via a further passive optical distribution network to a node (K1, . . . , Km). Each node (K1, . . . , Km,) includes means for separating the information received from the customer locations into, e.g.

Abstract: The thermo-optic behavior of an optical path over a range of temperatures &Dgr;T is controlled by determining a figure-of-merit (FOM) for the optical path and including in the path a body of crystalline material that enables the conditions specified by the FOM to be satisfied. The crystalline material is highly transparent at a wavelength &lgr; of radiation propagating in the path, and it has a coefficient of thermal expansion (CTE) and a refractive index n such that the CTE and dn/dT are mutually adapted to satisfy the FOM over the range &Dgr;T. In one embodiment, the CTE and dn/dT of an etalon compensate one another so as to perform frequency discrimination that is essentially temperature insensitive over the range &Dgr;T. In a preferred embodiment of the optical etalon the crystalline material comprises LiCaAlF6.

Abstract: A device that includes a projection element positioned between first and second beam scanners configured in series and a two-dimensional display plane. An apparatus for controlling the first and second beam scanners is provided so that the angle of incidence and the point of incidence of a beam output from the series connected beam scanners onto the projection element are controlled. In that manner, each point on the projection element can be mapped to a line in the display plane. A method of mapping a point in the projection element to a line in the display plane is also disclosed.

Abstract: A transparent pane arrangement with a prescribed installation alignment comprises at least one transparent substrate and at least two mutually spaced layers made from a material with variable transmission properties for visible light and/or thermal radiation. Both layers respectively have strips which are arranged parallel to one another and are made from the material with variable transmission properties.

Abstract: An optical component is disclosed. The optical component includes a light signal carrying region positioned between secondary regions. The component also includes a thermal conductor positioned over the light signal carrying region and at least a portion of the secondary regions. The thermal conductor includes one or more nanotubules. In some instances, the nanotubules are formed by applying microwaves to a material such as carbon.

Abstract: An optical element, optical control device and optical control method are provided which demonstrate a large, rapid optical response using a laser light of low output as a control light. A signal light 1 is emitted from an optical source 1. A signal light 2 emitted from an optical source 2. A control light and the signal light are converged by a condenser lens 7, and irradiate an optical element 8. Only the signal light is detected by a photodetector 22 through a light receiving lens 9 and a wavelength selection filter 20. A thermal lens is formed reversibly in the optical element and switching the control light ON and OFF modulates the intensity of the signal light.

Abstract: The optical transmission apparatus for multiple wavelengths according to the present invention comprises; a light source, a temperature control section for controlling the temperature of the light source, a temperature control (ATC) loop for controlling the operation of the temperature control section, and a wavelength control (AFC) loop. The ATC loop detects the temperature of the light source and feedback controls the operation of the temperature control section, so that the optical output wavelengths of the light source fall within a wavelength capture range corresponding to a target wavelength of the AFC loop. The AFC loop has a wavelength detection filter having a periodic transmission wavelength characteristic.

Abstract: An optical signal filter for providing a periodic transfer function in transmitting signals within a selected bandwidth, by which passbands are interleavered into groups of separate outputs. The filter employs the transmissivity characteristic of birefringent crystals in conjunction with splitting the input beam into orthogonal and separate components, while compensating for temperature variations by pairing crystals of different types. The transmissivity functions are independent of the polarization of the input beam, and are shaped to flatten transmissivity peaks by the use of cascaded stages of birefringent crystal pairs.

Abstract: A luminous intensity sensor element having a flat disk-shaped element (2) made of material with a high thermal expansion coefficient and of low thermal conductivity, and in turn having, on opposite faces (3, 5), an optically absorbent layer (4) and a reflecting layer (6). On receiving excitation radiation (R), the optically absorbent layer (4) is heated and transmits heat to the flat disk-shaped (2), which in turn is heated internally in spatially nonuniform manner and is deformed together with the superimposed reflecting layer (6). The reflecting layer (6) receives an incident reference layer beam (S) to generate a reflected light beam having optical characteristics (&Dgr;&phgr;) depending on the aforementioned deformation (&Dgr;d) and varying in response to the excitation radiation.

Abstract: A thermo-optical device to alter the direction and/or intensity of a light beam is described. In the thermo-optical device, a first material in contact with a second material defines an interface therebetween. The first and second materials have disparate thermo-optical coefficients such that, at a first temperature, the refractive indices of the two materials are the same and, at a second temperature, the refractive index of one material is less than the refractive index of the other material. At the first temperature, when the two refractive indices are equal, a light beam incident on the interface is transmitted through the interface without refraction. At the second temperature, the light beam propagating through one of the material, if incident on the interface at an appropriate angle, will be reflected off, instead of transmitted through, the interface.

Abstract: The invention concerns an electrochromic glazing system, with an electrochromic pane unit and at least one other pane, which are joined to one another in the edge area by means of a spacer frame, forming an interspace, and with a temperature sensor for detection of the temperature of the electrochromic pane unit. To optimize its location, according to the invention the temperature sensor is arranged in the region of the spacer frame, between the electrochromic pane unit and the other pane. The invention takes advantage of the fact that the spacer frame area represents a thermal bridge between the panes of a double-glazing unit which is especially suitable for the arrangement of a temperature sensor.

Abstract: A thermochromic game or prize or message indicator includes a typical thermochromic or thermally sensitive battery testers coupled to a first conductive substrate with a second thermally responsive game piece or prize or message indicator of the present invention combines a typical thermochromic or thermally sensitive battery tester coupled to the conductive substrate with an extension of the conductive substrate. The thermochromic game or prize of message indicator can be used to display a verbal message or icon for conveying whether a prize has been won. Additionally, the thermochromic game or prize or message indicator can be used to display any desired verbal message or icon.

Abstract: The thermooptic modulator includes a wave guide (1) having a switching section (4), a refracting section (5) bordering the switching section (4) and extending transversely to a signal propagation direction (14) in the wave guide and a first heating element (8) extending on the refracting section (5) along a boundary (6) between the wave guide (1) and the refracting section (5). In order to improve signal suppression when the modulator is switched to an impermable state, a second heating element (9) is provided extending on the wave guide (1) along the boundary (6).

Abstract: A thermo-optic semiconductor device has one semiconductor region providing an optical waveguide and an adjacent semiconductor region providing a resistive heater between two doped regions, current may be passed through the resistive heater within the adjacent semiconductor region to heat it and thereby vary the optical characteristics of the waveguide.

Abstract: A conductive composition is disclosed. The conductive composition comprises a thermochromic material and a conductive material dispersed in a resin. An electrical system is also disclosed which incorporates the conductive composition in combination with a power source.

Abstract: Devices that comprise novel, mesoscopically periodic materials that combine crystalline colloidal array (CCA) self-assembly with the temperature ined volume phase transitions of various materials, preferably poly(N-isopropylacrylamide) (PNIPAM) are disclosed. In one embodiment, a PNIPAM CCA is formed in an aqueous media and contained within cell means. In another embodiment, a CCA of charged particles is formed and polymerized in a PNIPAM hydrogel. Methods for making these devices are also disclosed. The devices of the present invention are useful in many applications including, for example, optical switches, optical limiters, optical filters, display devices and processing elements. The devices are further useful as membrane filters. All of these devices have the feature of being tunable in response to temperature. Devices that change diffracted wavelength in response to pressure are also disclosed.

Abstract: A display device utilizes a plurality of pixels arranged in a predetermined configuration for recording and displaying information. Each pixel includes a substrate and a light modulating material for selectively modulating a predetermined wave length of light by transitioning between a first and a second state in response to a heater element. The light modulating material in the first state causes destructive interference in the predetermined wave length of light and in the second state causes constructive interference in the predetermined wave length of light. The pixel structure is buried within an aerogel thereby minimizing the heat dissipation rate from the pixels.

Abstract: A light-reactive thermal window is disclosed having external and internal panes. The external pane is composed of photochromic glass, while the internal pane is composed of clear glass. The panes are separated by a space having a uniform thickness. Each of the panes has a peripheral edge, with a spacer located between the peripheral edges of the external and internal panes. A sealant seals the peripheral edges of the external and internal panes. The window may include a frame securing together the spacer, the sealant, and the peripheral edges of the panes. Also disclosed is a method of preventing glare on a screen while minimizing climate control costs by installing a light-reactive thermal window near the screen.

Abstract: Devices that comprise novel, mesoscopically periodic materials that combine crystalline colloidal array (CCA) self-assembly with the temperature ined volume phase transitions of various materials, preferably poly(N-isopropylacrylamide) (PNIPAM) are disclosed. In one embodiment, a PNIPAM CCA is formed in an aqueous media and contained within cell means. In another embodiment, a CCA of charged particles is formed and polymerized in a PNIPAM hydrogel. Methods for making these devices are also disclosed. The devices of the present invention are useful in many applications including, for example, optical switches, optical limiters, optical filters, display devices and processing elements. The devices are further useful as membrane filters. All of these devices have the feature of being tunable in response to temperature. Devices that change diffracted wavelength in response to pressure are also disclosed.

Abstract: In a digital thermo-optic switch and an optical ADM filter of the present invention, functional components such as a splitter and a grating structure part formed in the course of an optical circuit as a component are composed of silicone materials which are superior in heat resistance, reduced loss, and low birefringence, thereby achieving sufficiently practical thermal stability, low loss at 1.55 to 1.58 .mu.m band, wavelength selectivity, and cost reduction.

Abstract: The invention is an energy efficient, thermochromic device for windows that allows sunlight or solar radiation into a building or structure when the ambient temperature is low and substantially blocks solar radiation when the ambient temperature is high, especially when sunlight is directly on the window. Additionally, the invention is a thermochromic device useful as variable transmission shutters for use in lenses or filters.

Abstract: The recording of an image is performed on a heat-mode sensitive material by an optical modulator equipped with an optical modulation element consisting of an electro-optic crystal substrate. An optical modulation element 10 has an electro-optic crystal substrate 11 consisting of PLZT ceramic. The optical modulation element 10 is arranged on a base plate 18 consisting of aluminum (Al). The base plate 18 is arranged on cooling mechanism 20 that cools the electro-optic crystal substrate 11. Temperature detection mechanism 23 for detecting the temperature of the electro-optic crystal substrate 11 is provided in a portion of the base plate 18. Control mechanism is provided for controlling the cooling mechanism 20 so that the temperature of the electro-optic crystal substrate 11 becomes constant, based on temperature information from the temperature detection mechanism 23.

Abstract: A laminated body comprising an aqueous solution, in which molecules dissolved in water aggregate upon increasing temperature to demonstrate cloudy light-scattering resulting in decrease in light transmittance, sealed between two substrates which are at least partially transparent to allow direct visibility of said aqueous solution, wherein said aqueous solution comprises 0.5 to 45 parts by weight of an amphipathic substance which exhibits a clouding point, is an oil at room temperature and dissolves uniformly in water at room temperature, dissolved in 100 parts by weight of a solution of 0.5 to 40 parts by weight of an ionic water-soluble polymer or a vinyl-based non-ionic water-soluble polymer exhibiting no clouding point at a temperature of not higher than about 45.degree. C. in 100 parts by weight of water, and said aqueous solution undergoes a temperature-dependent reversible sol-emulsion phase transition, as well as a window employing it.

Abstract: Devices that comprise novel, mesoscopically periodic materials that combine crystalline colloidal array (CCA) self-assembly with the temperature ined volume phase transitions of various materials, preferably poly(N-isopropylacrylamide) (PNIPAM) are disclosed. In one embodiment, a PNIPAM CCA is formed in an aqueous media and contained within cell means. In another embodiment, a CCA of charged particles is formed and polymerized in a PNIPAM hydrogel. Methods for making these devices are also disclosed. The devices of the present invention are useful in many applications including, for example, optical switches, optical limiters, optical filters, display devices and processing elements. The devices are further useful as membrane filters. All of these devices have the feature of being tunable in response to temperature. Devices that change diffracted wavelength in response to pressure are also disclosed.

Abstract: The present invention is in the field of optical components, more particularly, polymeric optical components, even more particularly, thermo-optical components, electro-optical components or passive components. The present invention pertains to an optical component having an at least penta-layered polymer structure on a substrate comprising:A) a low refractive index lower cladding layer,B) a core-matching refractive index lower cladding layer,C) a core layer,D) a core-matching refractive index upper cladding layer, andE) a low refractive index upper cladding layer.With this specific layer structure an optimum traversal confinement can be obtained, which results in less loss of light and an improved switching efficiency.

Abstract: A multilayered thermochromic display system is provided, wherein a thermochromic substance is applied to inert films in stacked layers with a non-invasive barrier between each layer of thermochromic substance. The thermochromic substance in each layer responds in a different temperature range so that as the temperature changes, the display exhibits repeated sequences of colors. The use of multiple layers with different temperature sensitivities enables the use of the displays over a broad range of temperatures.

Abstract: An optical shutter apparatus includes a source of illumination and a first aperture plate positioned in a path of light from the source of illumination. A cantilever shutter is positioned at each aperture in the aperture plate and includes at least two bonded layers, one being an electrically resistive layer which exhibits a first thermal coefficient of expansion (TCE) and the second layer exhibiting a second TCE that is different from the first TCE. A proximal end of the bonded layers is attached to the aperture plate at each aperture and a distal portion thereof covers the respective aperture when in position thereover. A controller applies signals to the first electrically resistive layer to cause a heating of the first and second layers and a resultant unequal expansion thereof. The expansion causes a flexure of the cantilever shutter and moves the distal portion thereof to either cover or uncover the aperture, which, when uncovered, allows transmission of the illumination therethrough.

Abstract: An elongated optic (12) is supported within a cylindrical housing (18) by a pair of support rods (14) passing through the cylindrical housing (18). A resilient retention spring (16) diametrically opposed to each support rod (14) presses the elongated optic (12) against the support rod (14) to prevent movement by the elongated optic (12) while allowing the elongated optic (12) to expand and contract. Contact between the support rods (14) and the resilient retention spring (16) is minimized to prevent inhibiting the internal reflectivity of the elongated optic.

Abstract: The present invention describes a self-responding laminated body in which an isotropic solution, wherein a polysaccharide derivative, dissolved in water, aggregates to demonstrate cloudy scattering due to a rise in temperature resulting in a decrease in optical transmittance, is sealed in a cell, of which at least a portion is transparent, that enables the aqueous solution to be viewed directly; wherein, the isotropic aqueous solution is a solution in which 100 parts by weight of a polysaccharide derivative, having a weight average molecular weight of roughly 10,000 to roughly 200,000, is dissolved in roughly 110 to roughly 2,000 parts by weight of a water-based medium composed of an amount of water that is roughly 25 to roughly 450 parts by weight with respect to 100 parts by weight of the polysaccharide derivative, and an amphipathic substance.

Abstract: Vanadium dioxide (VO.sub.2) based infrared spatial light modulators (SLM) in four embodiments are disclosed:(1) A VO.sub.2 thin film is deposited on a planar diode array. Each diode constitutes a "pixel" of the SLM. Power provided to a diode permits accurate thermal control about the thin film's hysteresis. Initial biasing of the diode array is required to the base of the VO.sub.2 's hysteresis curve.(2) & (3) VO.sub.2 is deposited on a thermoelectric array which can be an array of doped lines of p and n type material or a conductive material between two electrical contacts. The pixels have the ability to both heat and cool the VO.sub.2 film, thereby allowing the array to be operated in a bistable mode. Bistable operation requires external biasing to the center of the VO.sub.2 's hysteresis curve.(4) A VO.sub.2 thin film deposited on a substrate which is spaced a distance, L, from an array of vertical-cavity surface-emitting lasers for heating the VO.sub.2.

Abstract: The ellipticity of a thermal lens is controlled in a diode-pumped anisotropic crystal, such as Nd:YVO4. The crystal has two opposing optical end faces through which a pump beam and an output beam pass. The crystal also has opposing "c" axis crystal faces normal to a "c" axis of the crystal, and opposing "a" axis crystal faces that are normal to an "a" axis of the crystal. A mount supports the crystal and serves as a heat sink. A path is created to conduct heat from the crystal through the "c" faces, while the "a" faces are thermally isolated from heat conduction. The thermal lens ellipticity is controlled in order to produce a round, diffraction limited gaussian beam suitable for applications that require a high power, good quality beam from a simple, reliable laser source.

Abstract: The present invention provides a bistable optical device in which the active medium is a polymer material of thermo-optical effect inserted into a cavity resonator, preferably a FABRY-PEROT resonance cavity, in said cavity the polymer material transmitting and reflecting an incident light wave with bistable values and values variable according to its thermal state. This latter is varied by the absorption of a fraction of the incident light wave, which transfers heat to the polymer material to generate therein an increase in the transmission of the incident light and a variable refractive index in response to the increase in its temperature, to thus provide a positive response effect which enables the device of the present invention to vary between two bistable states.

Abstract: A tunable optical filter for use in wavelength division multiplexing systems. The optical filter contains a plurality of tunable reflection gratings which block all of the channels in the incoming lightwave. An electrode or a heating element is provided for each reflection grating to tune the reflection gratings so that their reflection bands do not coincide with a desired channel or channels thereby allowing the desired channel or channels to pass through the filter.

Abstract: A heat sensitive system comprises a document having a localized, non-pressure sensitive, coating of chromogenic composition activated at moderate temperatures. Quickly striking the chromogenic composition with a fingernail or blunt object produces a colored image by frictional heat. The chromogenic composition contains a chromogenic compound and a color developer which are non-pressure sensitive and non-reactive at room temperature. The chromogenic composition can be an intimate mixture of the chromogenic compound and the developer or alternatively separate layers of each of the components.

Abstract: A printed document, such as a lottery ticket, includes a thermochromic layer at least over the imprinted data region. The printed document can be authenticated by applying heat to the thermochromic material and observing the presence or absence of a reversible color change.