Abstract: The invention relates to the field of algae biofuel production, in particular to methods and means of physical action on biological structures of photosynthesing microorganisms, phototrophic algae in particular. The invention can be used for obtaining biofuel from algae, as well as for the pharmaceutical, cosmetic and foodstuff industries. In the process of the method implementation radiation of cultivated solution of photosynthesizing microorganisms/phototrophical algae is carried out by the action of electromagnetic waves of a selected intensity. Stimulation of increasing photosynthesizing microorganisms/phototrophical algae biomass is obtained by the interaction of electromagnetic wave and biological cell. Irradiation of cultivated solution of photosynthesizing microorganisms/phototrophical algae is performed by electromagnetic waves originating from specified sensor mechanisms mounted about the acrylic or plastic-based stackable tubular bioreactor.

Abstract: A method of phase modulating optical radiation by the steps of phase modulating the optical radiation by using a modulator having an extinction ratio in order to provide a multilevel phase shift key signal, and applying to each optical pulse a phase-shift having an absolute value depending on the extinction ratio and a sign depending, for each of the optical pulses, on the respective optical phase value. An apparatus implementing the method is also disclosed.

Abstract: In various embodiments, an interferometric display device includes a plurality of structures that redirect light from an inactive area of the display to an active area of the display. Light incident on the structures that would normally continue towards an inactive area of the display is either reflected, refracted, or scattered towards an active area of the display including moveable and static reflective surfaces that form an optical cavity.

Abstract: A reflective display device including: a substrate; a reflective layer on the substrate and configured to reflect light incident on the reflective layer; a color filter layer on the reflective layer; and an optical shutter layer on the color filter layer. Each pixel of a plurality of pixels of the reflective display device includes a plurality of sub-pixels and each sub-pixel includes the substrate, the reflective layer, the color filter layer, and the optical shutter layer, and for each pixel, the color filter layer includes a plurality of color filter elements corresponding to colors respectively obtained by the plurality of sub-pixels.

Abstract: A light control device 1 includes a light source 10, a prism 20, a spatial light modulator 30, a drive unit 31, a control unit 32, a lens 41, an aperture 42, and a lens 43. The spatial light modulator 30 is a phase modulating spatial light modulator, includes a plurality of two-dimensionally arrayed pixels, is capable of phase modulation in each of these pixels in a range of 4?, and presents a phase pattern to modulate the phase of light in each of the pixels. This phase pattern is produced by superimposing a blazed grating pattern for light diffraction with a phase modulation range of 2? or less and a phase pattern having a predetermined phase modulation distribution with a phase modulation range of 2? or less.

Abstract: A color display has continuous areas of a single color covering a plurality of sub-pixel electrodes. Each sub-pixel of a given color has sub-pixels of the same given color disposed along at least two of its adjacent edges. Each area of a single color may cover a 2×2 array of sub-pixel electrodes.

Abstract: An electro-optic display comprises, in order, a light-transmissive electrically-conductive layer; a layer of a solid electro-optic material; and a backplane (162) bearing a plurality of pixel electrodes, a peripheral portion of the backplane extending outwardly beyond the layer of solid electro-optic material and bearing a plurality of radiation generating means (166) and a plurality of radiation detecting means (168), the radiation generating means and radiation detecting means together being arranged to act as a touch screen.

Abstract: A system and method for producing an 8-QAM-modulated signal are disclosed. The methodology, in an exemplary expedient, generally comprises splitting light from a CW laser into two parts; modulating the first part with a first signal and modulating the second part with a second signal; phase shifting the modulated second part by about ?/4; combining the modulated first part with the phase shifted and modulated second part to produce a four-level modulated signal; and phase modulating the four-level modulated signal with a third signal with a phase modulation of (0, ?/2). Several variations of this method are described herein.

Abstract: Described are a method and apparatus for high-speed phase shifting of an optical beam. A transparent plate having regions of different optical thickness is illuminated by an optical beam along a path of incidence that extends through the regions. The transparent plate can be moved or the optical beam can be steered to generate the path of incidence. The optical beam exiting the transparent plate has an instantaneous phase value according to the region in which the optical beam is incident. Advantageously, the phase values are repeatable and stable regardless of the location of incidence of the optical beam within the respective regions, and phase changes at high modulation rates are possible. The method and apparatus can be used to modulate a phase difference of a pair of coherent optical beams such as in an interferometric fringe projection system.

Abstract: A system and method for producing a 16-QAM-modulated signal are disclosed. The methodology, in an exemplary expedient, generally comprises splitting light from a CW laser into two parts; modulating the first part with a first signal and modulating the second part with a second signal; phase shifting the modulated second part by about ?/2; combining the modulated first part with the phase shifted and modulated second part to produce a four-level modulated signal; phase modulating the four-level modulated signal with a third signal with a phase modulation of about (0, ?/2) to produce an 8-QAM-modulated signal, and thereafter modulating that signal with a fourth signal with a phase-modulation of about (0, ?) to produce the 16-QAM-modulated signal.

Abstract: Various types of edge seals for protecting electro-optic displays against environmental contaminants are described. In one type of seal, the electro-optic layer is sandwiched between a backplane and a protective sheet and a sealing material extends between the backplane and the protective sheet. In other seals, the protective sheet is secured to the backplane or to a second protective sheet adjacent the backplane. The electro-optic layer can also be sealed between two layers of adhesive or between one layer of adhesive and the backplane. Other seals make use of flexible tapes extending around the periphery of the display.

Abstract: Various types of edge seals for protecting electro-optic displays against environmental contaminants are described. In one type of seal, the electro-optic layer is sandwiched between a backplane and a protective sheet and a sealing material extends between the backplane and the protective sheet. In other seals, the protective sheet is secured to the backplane or to a second protective sheet adjacent the backplane. The electro-optic layer can also be sealed between two layers of adhesive or between one layer of adhesive and the backplane. Other seals make use of flexible tapes extending around the periphery of the display.

Abstract: A device that provides light beam switching, agile steering of the light beam over a range of angles, and generation of arbitrary wavefront shapes with high spatial and temporal resolution. The agile device can include a volume diffractive structure comprising Bragg planes having one refractive index and the Bragg planes separated by regions containing an active optical medium. Electrodes (which may be the Bragg planes themselves, or may be arrayed adjacent to the active optical medium) are used to control the electric field intensity and direction across the structure, and thereby control the diffraction efficiency of the structure and the local phase delay imposed on a diffracted wavefront. Means are provided for addressing the many thousands of electrodes required for precise and rapid wavefront control. Applications include free-space atmospheric optical communications, near-eye displays, direct-view 3D displays, optical switching, and a host of other applications.

Abstract: Various types of edge seals for protecting electro-optic displays against environmental contaminants are described. In one type of seal, the electro-optic layer is sandwiched between a backplane and a protective sheet and a sealing material extends between the backplane and the protective sheet. In other seals, the protective sheet is secured to the backplane or to a second protective sheet adjacent the backplane. The electro-optic layer can also be sealed between two layers of adhesive or between one layer of adhesive and the backplane. Other seals make use of flexible tapes extending around the periphery of the display.

Abstract: A system for delivering more than one optical power form and at least one control signal over an optical conduit includes control circuitry for controlling characteristics of the optical power system.

Abstract: A system for delivering optical power over an optical conduit includes at least one optical power source delivering multiple optical power forms, at least one of the optical power forms being a modulated optical power form. The system includes an optical power receiving device that is directly driven by the at least one modulated optical power form.

Abstract: An illumination obscurement device for controlling the obscurement of illumination from a light source which is optimized for use with a rectangular, arrayed, selective reflection device. In a preferred embodiment, a rotatable shutter with three positions is placed between a light source and a DMD. The first position of the shutter is a mask, preferably an out of focus circle. This out of focus circle creates a circular mask and changes any unwanted dim reflection to a circular shape. The second position of the shutter is completely open, allowing substantially all the light to pass. The third position of the shutter is completely closed, blocking substantially all the light from passing. By controlling the penumbra illumination surrounding the desired illumination, DMDs can be used in illumination devices without creating undesirable rectangular penumbras.

Abstract: A method includes generating a plurality of beams that each illuminate a separate portion of a spatial light modulator. The spatial light modulator has a first dimension of a first length and a second dimension of a second length. Each of the beams spans a portion of the first length of the first dimension and a portion of the second length of the second dimension. The method also includes scrolling the plurality of beams along the second dimension of the spatial light modulator while maintaining at least a first gap between each of the plurality of beams.

Abstract: An image capturing device includes a base formed with a first receiving space defined by a bottom wall and a first surrounding wall, and a second receiving space defined by a top side of the first surrounding wall and a second surrounding wall. A lens module is mounted on the base for generating an optical image of an object. An auto-focusing module is disposed in the second receiving space for auto-focusing the optical image based on an external voltage. A sensing module is mounted in the first receiving space and on the bottom wall of the base, is disposed under the auto-focusing module, and is spaced apart from the lens module at a predetermined distance for sensing the optical image focused by the auto-focusing module so as to generate an electrical output corresponding to the optical image.

Abstract: An optical device includes multiple reflective spatial light modulation devices each of which applies an image signal to each of rays of incident light and rotates a polarization direction of each of the rays of incident light for a modulated output, multiple polarization elements each of which causes each polarization component of the rays of incident light in a specific direction to be transmitted and incident upon each of the spatial light modulation devices and reflects the polarization component in a direction rotated by each of the spatial light modulation devices, a light synthesis device which synthesizes multiple rays of reflected light to be output as one ray of image light, and a securing member which simultaneously secures each of the polarization elements in a position corresponding to each of the spatial light modulation devices. The securing member is secured to the light synthesis device.

Abstract: A spatial light modulator comprises an integrated optical compensation structure, e.g., an optical compensation structure arranged between a substrate and a plurality of individually addressable light-modulating elements, or an optical compensation structure located on the opposite side of the light-modulating elements from the substrate. The individually addressable light-modulating elements are configured to modulate light transmitted through or reflected from the transparent substrate. Methods for making such spatial light modulators involve fabricating an optical compensation structure over a substrate and fabricating a plurality of individually addressable light-modulating elements over the optical compensation structure. The optical compensation structure may be a passive optical compensation structure.

Abstract: Techniques for producing higher fidelity interferometer measurements by reducing sensitivity to spurious sources include reducing the coherence length of an electromagnetic beam. In addition, multiple surfaces within an optical system may be measured by electronically tuning the position of a coherence plane along the optical paths of an interferometer. A phase modulator is used in conjunction with a long coherence length electromagnetic source to generate beams for each leg of an interferometer. Providing a controlled broadband RF signal to the phase modulator increases the bandwidth of the beam and thereby reduces the coherence length of the beam. This reduces the spurious contributions to the output interference fringes from undesired surfaces along the beam path.

Abstract: One exemplary metamaterial is formed from a plurality of individual unit cells, at least a portion of which have a different permeability than others. The plurality of individual unit cells are arranged to provide a metamaterial having a gradient index along at least one axis. Such metamaterials can be used to form lenses, for example.

Abstract: A tunable dispersion compensator (TDC) is tuned from a first dispersion setpoint to a second dispersion setpoint while maintaining continuity of the dispersion.

Abstract: A source of terahertz radiation at a fundamental terahertz frequency is tunable over a fundamental terahertz frequency range, and is coupled into a first waveguide. The first waveguide supports only a single transverse spatial mode within the fundamental terahertz frequency range. A solid-state frequency multiplier receives from the first waveguide the terahertz radiation and produces terahertz radiation at a harmonic terahertz frequency. A second waveguide receives the harmonic terahertz radiation. The tunable terahertz source can comprise a backward wave oscillator with output tunable over about 0.10-0.18 THz, 0.18-0.26 THz, or 0.2-0.37 THz. The frequency multiplier can comprises at least one varistor or Schottky diode, and can comprise a doubler, tripler, pair of doublers, doubler and tripler, or pair of triplers. The terahertz source can be incorporated into a terahertz spectrometer or a terahertz imaging system.

Abstract: An optical signal generator includes a single-mode laser; a reflecting mirror to define another cavity different from a cavity of the single-mode laser, and reflect a part of output light from the single-mode laser to return the part of the output light to the single-mode laser; an intensity modulator provided between the single-mode laser and the reflecting mirror; and a phase adjuster, provided between the single-mode laser and the reflecting mirror, to adjust a frequency difference between a signal on state and a signal off state generated in accordance with intensity modulation by the intensity modulator.

Abstract: A microlouver includes a periodic structure in which a transparent layer and a light absorption layer are alternately disposed with a constant, repetitive period. The range of the exit direction of a light beam passing through the transparent layer is restricted by the light absorption layer. The periodic structure includes a periodic structure portion divided in the direction that intersects the direction in which the transparent layer and the light absorption layer are repeatedly disposed. In the periodic structure portion, between the periodic structures adjacent to each other, there is a difference of 180 degree in the phase of spatial frequency of each periodic structure.

Abstract: In a conventional optical signal processing device, a confocal optical system is configured in which a focusing lens is positioned at a substantially-intermediate point of a free space optical path. Thus, the free space optical system had a long length. It has been difficult to reduce the size of the entire device. The optical signal processing device of the present invention uses a lens layout configuration different from the confocal optical system to thereby significantly reduce the length of the system. The optical signal processing device consists of the first focusing lens positioned in the close vicinity of a signal processing device, and the second focusing lens positioned in the vicinity of a dispersing element. A distance between the dispersing element and the signal processing device is approximately a focal length of the first focusing lens. Compared with the conventional technique, the length of the optical path can be halved.

Abstract: An image display apparatus includes a first optical modulation device and a second optical modulation device configured to emit linearly polarized lights whose polarization directions are perpendicular to each other, first pixels and second pixels are arranged in each of the first optical modulation device and second optical modulation device, retardation layers are disposed on the light emission side of the first pixels or second pixels, the retardation layers configured to convert one linearly polarized light of the linearly polarized lights into the other linearly polarized light. Either arrangements of the first pixels and the second pixels or arrangements of the retardation layers is set so as to be the same in the first optical modulation device and the second optical modulation device, and the other is set so as to be the reverse in the first optical modulation device and the second optical modulation device.

Abstract: Techniques, devices and systems based on optical receivers with controllable transfer function bandwidth and gain imbalance.

Abstract: A transmissive backlit display is disclosed. In one aspect, the backlit display comprises a backlight and an array of transmissive interferometric modulators. Each interferometric modulator comprises a fixed and moving dielectric mirror stack. The interferometric modulators cause light within the desired wavelength range to be transmitted while reflecting at least a portion of the remaining light.

Abstract: The invention concerns a Optical modulator, comprising an input suitable to receive an optical carrier, a high-frequency input and an output suitable to transmit an optical signal, the optical modulator comprising two Mach-Zender (1,2) modulators in parallel between the input and output, which constitute two different optical paths, the whole circuit constituting a third Mach-Zender modulator (3), the optical modulator being characterised in that: the first Mach-Zender modulator (1) is provided with an electrode suitable to carry, inside the modulator (1), two signals (RF1, RF2), each obtained by the sum of the two tones fR and fD, of equal power but dephased of ?/2, being further provided an electrode (Bias 1) for realising a Single Side Band modulation of the tones fR and fD; the second Mach-Zender modulator (2) is provided with an electrode (Bias 2) to realise statically a phase inversion of the optical carrier; the third Mach-Zender modulator (3) comprising an electrode (Bias 3) suitable to realise the

Abstract: Speckle reduction apparatus includes a radiation path and a mask arranged within the radiation path. The mask includes an array of electrically controllable cells configured to form a pattern on the mask that varies with time. The speckle reduction mask includes a first linear array including first parallel lines arranged to change the phase of incident radiation, and a second linear array including second parallel lines arranged to change the phase of incident radiation and further arranged such that cells are formed at the intersections of the first parallel lines and the second parallel lines. The speckle reduction mask includes a N1×N2 array of cells, A, formed according to: ATA=??k,l, where AT is the transpose of A, ? is a real and positive constant, dk,l is Kronecker delta and N1?N2.

Abstract: An edge lit locally dimmed display has a spatial light modulator illuminated by a light source. The light source is positioned at an edge and behind the spatial light modulator. The spatial light modulator is illuminated with a low resolution version of a desired image. The illumination may comprise a series of lighting elements that vary smoothly from one element to another at the spatial light modulator.

Abstract: An image display system includes display element 13 that displays at least two display states at different timings, the two display states being a first display state in which a first image is displayed with a first polarized light and a second image is displayed with a second polarized light whose polarized component is different from that of the first polarized light, the second image serving to cancel the first image, and a second display state in which the second image is displayed with the first polarized light and the first image is displayed with the second polarized light; and optical shutter 14 that transmits the first polarized light and blocks the second polarized light in the first display state and transmits the second polarized light and blocks the first polarized light in the second display state.

Abstract: A laser is placed inside the Mach-Zehnder interferometer and the output from opposite ends of the laser are fed directly into the opposite arms of the Mach-Zehnder interferometer. If the output from opposite sides of the laser are equal in amplitude and wavelength, then when the outputs are recombined at the output of the modulator the intensity is dependent on the relative phase of the light in the two arms of the Mach-Zehnder, just as in a normal Mach-Zehnder modulator. Thus by modulating the phase of one or both arms of the modulator, an intensity modulated source is created. This reduces the overall size of the device, and may ensure that all of the output power from the laser is utilized.

Abstract: In an aberration-correcting method according to an embodiment of the present invention, in an aberration-correcting method for a laser irradiation device 1 which focuses a laser beam on the inside of a transparent medium 60, aberration of a laser beam is corrected so that a focal point of the laser beam is positioned within a range of aberration occurring inside the medium. This aberration range is not less than n×d and not more than n×d+?s from an incidence plane of the medium 60, provided that the refractive index of the medium 60 is defined as n, a depth from an incidence plane of the medium 60 to the focus of the lens 50 is defined as d, and aberration caused by the medium 60 is defined as ?s.

Abstract: When designing a demodulator for a DPSK-modulated signal, it is required that optical phase modulation is performed fast and the demodulator has a long lifetime. To achieve this object, a delay line interferometer inside the demodulator performs adjustment of phase difference between two split lights caused to interfere, using a first optical phase modulation unit such as a Piezo actuator and a second optical phase modulation unit such as a heating element that operates slower in modulation speed than the first optical phase modulation unit and is slower in deterioration speed.

Abstract: A 2n-QAM (e.g. 16-QAM) optical modulator comprising cascaded I-Q modulators. The first I-Q modulator applies 2n?2 (e.g. 4) QAM to an optical signal, having a constellation diagram with the 2n?2 (e.g., 4) constellation points located in quadrant I. The second I-Q modulator subsequently applies a quaternary phase-shift keying (QPSK) modulation scheme to the optical signal, thereby rotating the constellation points of the 2n?2-QAM modulation scheme to quadrants II, III and IV, to produce a 2n-QAM modulation constellation diagram. The rotation causes the 2n-QAM modulator to inherently apply four quadrant differential encoding to the optical signal. A method of 2n-QAM optical modulation is also provided and optical signal transmission apparatus comprising the 2n-QAM optical modulator.

Abstract: The invention provides an illumination device (1), arranged to provide illumination device light (250). The illumination device (1) comprising a light chamber (100), an electrically variable scattering element (500), and a controller (600). The light chamber (100) contains a light emitting diode (10) (LED) arranged to emit LED light (20); comprises a luminescent material layer (200) arranged remote from the LED (10) and arranged to absorb at least part of the LED light (20) and emit luminescent material emission (220); and comprises an exit face (301), through which one or more of the LED light (20) and the luminescent material emission (220) may escape to the exterior (22) of the light chamber (100) thereby providing illumination device light (250). The electrically variable scattering element (500) is arranged downstream of the luminescent material layer (200) and upstream of the exit face (301).

Abstract: This optical mask is an optical mask which applies spatial intensity modulation to input light in a beam cross-section and outputs a light after being subjected to the modulation, and when regions A0 to Ap defined by circumferences with p radiuses r1 to rp (p is an even number, rp>rp?1> . . . >r2>r1, and rp?rp?1>rp?1?rp?2> . . . >r3?r2>r2?r1>r1) around a predetermined position are set in order from an inner side, a region Am (m is an even number not less than 0 and not more than p) is a light transmission region, and a region An (n is an odd number not less than 0 and not more than p) is a light shielding region.

Abstract: A switchable film assembly having remote electrical connections comprises an active layer between first and second electrically conductive layers. The active layer has an optical transmission which changes upon projecting an electric field therethrough. An electrical connection connects the film to a power supply and can comprise a remote electrical connector region provided remote to the first and second electrically conductive layers, such upon connecting the film assembly to the power supply, an electrical field may be projected through at least a portion of the switchable film assembly thereby changing the optical transmission of the active layer.

Abstract: A method of switching an electrically actuated variable transmission layer is disclosed. The layer is between a first electrode and a second electrode, and when a sufficiently high frequency alternating electric field is applied between the first and second electrodes, a selective region of the layer in between the first and second electrodes is switched. Apparatus for use as a glazing pane having a sheet of glazing material and an electrically actuated variable transmission layer facing the sheet of glazing material is also disclosed. The layer is sandwiched between a first electrode and a second electrode. There is an electric field generator in electrical communication with the electrodes and being configured to produce an alternating electric field of sufficient strength and of a sufficiently high frequency to switch a selected region of the layer in between the first and second electrodes.

Abstract: The present invention relates to an optical modulator that generates quaternary amplitude modulated light without inter-symbol-interference by splitting input light into three optical paths, generating a continuous wave signal in a first optical path, generating binary phase modulated lights using a single drive MZ type optical phase modulator in second and third optical paths, and interfering them at in-phase and at field amplitude 1:a:b.

Abstract: This invention provides an optical device comprising a large group of non-uniform resonators operating cumulatively as a ‘super-ring’ to provide a controllable group delay with large bandwidth. The super-ring tuning is performed by a single control. The device may include two super-rings, each includes a large number of resonators with a resonant frequencies centered around ?1 and ?2 respectively. The invention provides multiple ways to improve the delay duration, bandwidth and the tuning speed, and overcomes the issue of non-uniformity of resonance frequency for devices incorporating multiple optical resonators.

Abstract: A first apparatus for displaying a color image comprises an electro-optic display (1002) having a plurality of pixels, each of which can be independently set to a light-transmissive optical state or a substantially opaque optical state, and lighting means (1006) arranged to flash separate pulses of light of at least two differing colors on to one surface of the electro-optic display (1002). A second apparatus for generating pulses of light of differing colors comprising a light source and a filter assembly comprising first (1100) and second (1106) electro-optic layers each having a light-transmissive state and a colored state, the two colored states being different, and electrodes to switch these layers between these states.

Abstract: The present invention discloses a method and device for the bias control of an MZ modulator. The method comprises: during startup of an MZ modulator, inputting a linearly changing bias control voltage to the bias electrode of the MZ modulator and obtaining the output optical power of the MZ modulator so as to determine a bias control voltage corresponding to a preset operating point; then enabling a communication electrical signal to be input to the radio frequency electrode of the MZ modulator, carrying out an amplitude modulation on the communication electrical signal by a low-frequency sinusoidal pilot signal, and inputting the determined bias control voltage to the bias electrode simultaneously; and sampling the output optical signals of the MZ modulator, comparing the sampled optical signal with the pilot signal, and adjusting the bias control voltage input to the bias electrode according to the result of the comparison.

Abstract: In an embodiment, an optical filter device includes an input polarizer for selectively transmitting an input signal. The device includes a wave-plate structure positioned to receive the input signal, which includes first and second substantially zero-order, zero-wave plates arranged in series with and oriented at an angle relative to each other. The first and second zero-wave plates are configured to alter a polarization state of the input signal passing in a manner that depends on the power of the input signal. Each zero-wave plate includes an entry and exit wave plate each having a fast axis, with the fast axes oriented substantially perpendicular to each other. Each entry wave plate is oriented relative to a transmission axis of the input polarizer at a respective angle. An output polarizer is positioned to receive a signal output from the wave-plate structure and selectively transmits the signal based on the polarization state.

Abstract: A laser is placed inside the Mach-Zehnder interferometer and the output from opposite ends of the laser are fed directly into the opposite arms of the Mach-Zehnder interferometer. If the output from opposite sides of the laser are equal in amplitude and wavelength, then when the outputs are recombined at the output of the modulator the intensity is dependent on the relative phase of the light in the two arms of the Mach-Zehnder, just as in a normal Mach-Zehnder modulator. Thus by modulating the phase of one or both arms of the modulator, an intensity modulated source is created. This reduces the overall size of the device, and may ensure that all of the output power from the laser is utilized.

Abstract: A system and method for securing contents displayed on a display device, and a device for viewing displayed content are provided. The system may include a first device and a communication module. The communication module may be adapted to communicatively connect the first device to the display device. The first device may be adapted to control, via the communication module, the display device to alternately display a first content and a second content. The second content may contain interference information. The device for viewing displayed content may be adapted to alternately let light through and shut off light. With the device for viewing displayed content, the first content displayed is viewable by an intended viewer while the second content displayed is un-viewable by the intended viewer.