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62-453: Liquid crystal on silicon ( LCoS or LCOS ) is a miniaturized reflective active-matrix liquid-crystal display or "microdisplay" using a liquid crystal layer on top of a silicon backplane. It is also known as a spatial light modulator . LCoS initially was developed for projection televisions , but has since found additional uses in wavelength selective switching , structured illumination , near-eye displays and optical pulse shaping. LCoS

124-774: A Ferroelectric LCoS display technology (known as Time Domain Imaging) available in QXGA , SXGA and WXGA resolutions which today is used for high resolution near-eye applications such as Training & Simulation, structured light pattern projection for AOI . Citizen Finedevice (CFD) also continues to manufacturer single panel RGB displays using FLCoS technology (Ferroelectric Liquid Crystals). They manufacture displays in multiple resolutions and sizes that are currently used in pico-projectors , electronic viewfinders for high end digital cameras, and head-mounted displays . Whilst initially developed for large-screen projectors, LCoS displays have found

186-442: A negative temperature coefficient like other gas discharge lamps. They are operated at low-voltage, high-current, DC and started by field emission with a high voltage pulse of 20 to 50kV. As an example, a 450 W lamp operates normally at 18 V and 25 A once started. They are also inherently unstable, prone to phenomena such as plasma oscillation and thermal runaway . Because of these characteristics, xenon short-arc lamps require

248-441: A shortwave UV blocking coating on the envelope and are sold as "ozone free" lamps. These "ozone free" lamps are used commonly in indoor applications, where proper ventilation is not easily accessible. Some lamps have envelopes made out of ultra-pure synthetic fused silica (such as "Suprasidh"), which roughly doubles the cost, but which allows them to emit useful light into the vacuum UV region . These lamps are normally operated in

310-524: A 10 GHz optical frequency comb was shaped by the POP to generate dark parabolic pulses and Gaussian pulses, at 1540 nm and 1560 nm, respectively. Structured light using a fast ferroelectric LCoS is used in 3D- superresolution microscopy techniques and in fringe projection for 3D- automated optical inspection . One of the interesting applications of LCoS is the ability to transform between modes of few-moded optical fibers which have been proposed as

372-431: A ceramic body and an integral reflector. They are available in many output power ratings with either UV-transmitting or blocking windows. The reflector options are parabolic (for collimated light) or elliptical (for focused light). They are used in a wide variety of applications, such as video projectors, fiber optic illuminators, endoscope and headlamp lighting, dental lighting, and search lights. Xenon short-arc lamps have

434-519: A channel with better than 1 GHz resolution possible. This is advantageous from a manufacturability perspective, with different channel plans being able to be created from a single platform and even different operating bands (such as C and L) being able to use an identical switch matrix. Additionally, it is possible to take advantage of this ability to reconfigure channels while the device is operating. Products have been introduced allowing switching between 50 GHz channels and 100 GHz channels, or

496-572: A consumer niche in the area of pico-projectors , where their small size and low power consumption are well-matched to the constraints of such devices. LCoS devices are also used in near-eye applications such as electronic viewfinders for digital cameras, film cameras, and head-mounted displays (HMDs) . These devices are made using ferroelectric liquid crystals (so the technology is named FLCoS) which are inherently faster than other types of liquid crystals to produce high quality images. Google's initial foray into wearable computing, Google glass, also uses

558-518: A digital LCoS display device, which features an array of pixels , each equivalent to the reflecting side of a single LCLV. These pixels on the LCoS device are driven directly by signals to modulate the intensity of reflected light, rather than a low intensity "writing light" source in the LCLV. For example, a chip with XGA resolution has an array of 1024×768 pixels, each with an independently addressable transistor. In

620-437: A highly efficient, low-insertion loss switch shown. This simple optical design incorporates polarisation diversity, control of mode size and a 4-f wavelength optical imaging in the dispersive axis of the LCoS providing integrated switching and optical power control. In operation, the light passes from a fibre array through the polarisation imaging optics which separates physically and aligns orthogonal polarisation states to be in

682-474: A liquid crystal layer, a reflective layer, and a silicon substrate. The liquid crystal layer controls the polarization of light that passes through it, while the reflective layer reflects the light back towards the optical system. The silicon substrate is used to control the individual pixels and provides the necessary electronics to drive the LCos panel. The light source is used to provide the necessary illumination for

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744-416: A mix of channels, without introducing any errors or "hits" to the existing traffic. More recently, this has been extended to support the whole concept of Flexible or Elastic networks under ITU G.654.2 through products such as Finisar's Flexgrid™ WSS. The ability of an LCoS-based WSS to independently control both the amplitude and phase of the transmitted signal leads to the more general ability to manipulate

806-524: A near-eye LCoS display. At CES 2018, Hong Kong Applied Science and Technology Research Institute Company Limited ( ASTRI ) and OmniVision showcased a reference design for a wireless augmented reality headset that could achieve 60 degree field of view (FoV). It combined a single-chip 1080p LCOS display and image sensor from OmniVision with ASTRI's optics and electronics. The headset is said to be smaller and lighter than others because of its single-chip design with integrated driver and memory buffer. LCoS

868-405: A peculiar discharge regime where the plasma was thermalized, that is, the electrons were not significantly hotter than the gas itself. Under these conditions a positive current-voltage curve was demonstrated. This allowed the larger common sizes such as 5 and 10 kW to operate directly from mains AC at 110 and 220 volts respectively without a ballast – only a series igniter was necessary to start

930-439: A proper power supply that operates without flickering in the flame, which could ultimately damage the electrodes. These are structurally similar to short-arc lamps except that the distance between the electrodes in glass tube is greatly elongated. When mounted within an elliptical reflector, these lamps are frequently used to simulate sunlight in brief flashes, often for photography. Typical uses include solar cell testing (with

992-545: A pure nitrogen atmosphere. All modern xenon short-arc lamps use a fused quartz envelope with thoriated tungsten electrodes. Fused quartz is the only economically feasible material currently available that can withstand the high pressure (25 atmospheres for an IMAX bulb) and high temperature present in an operating lamp, while still being optically clear. The thorium dopant in the electrodes greatly enhances their electron emission characteristics. Because tungsten and quartz have different coefficients of thermal expansion ,

1054-427: A result, the anode in a xenon short-arc lamp either has to be much larger than the cathode or be water-cooled, to dissipate the heat. The output of a pure xenon short-arc lamp offers fairly continuous spectral power distribution with a color temperature of about 6200K and color rendering index close to 100. However, even in a high pressure lamp there are some very strong emission lines in the near infrared, roughly in

1116-737: A screen or other surface. The optical system consists of a number of lenses, mirrors, and other optical components that are carefully designed and calibrated to provide the necessary magnification, focus, and color correction for the display system. The white light is separated into three components (red, green and blue) and then combined back after modulation by the 3 LCoS devices. The light is additionally polarized by beam splitters . Both Toshiba's and Intel's single-panel LCOS display program were discontinued in 2004 before any units reached final-stage prototype. There were single-panel LCoS displays in production: One by Philips and one by Microdisplay Corporation. Forth Dimension Displays continues to offer

1178-434: A single switching element (pixel) to each channel which means the bandwidth and centre frequency of each channel are fixed at the time of manufacture and cannot be changed in service. In addition, many designs of first-generation WSS (particularly those based on MEMs technology) show pronounced dips in the transmission spectrum between each channel due to the limited spectral ‘fill factor’ inherent in these designs. This prevents

1240-421: A small amount of mercury metal. In a pure xenon lamp, the majority of the light is generated within a tiny, pinpoint-sized cloud of plasma situated where the electron stream leaves the face of the cathode. The light generation volume is cone-shaped, and the luminous intensity falls off exponentially moving from cathode to anode. Electrons passing through the plasma cloud strike the anode, causing it to heat. As

1302-526: A truly diffraction-limited spot. Larger lamps are employed in searchlights where narrow beams of light are generated, or in film production lighting where daylight simulation is required. All xenon short-arc lamps generate substantial ultraviolet radiation . Xenon has strong spectral lines in the UV bands, and these readily pass through the fused quartz lamp envelope unlike the borosilicate glass used in standard lamps; fused quartz readily passes UV radiation unless it

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1364-399: Is a highly specialized type of gas discharge lamp , an electric light that produces light by passing electricity through ionized xenon gas at high pressure. It produces a bright white light to simulate sunlight , with applications in movie projectors in theaters , in searchlights , and for specialized uses in industry and research. For example, Xenon arc lamps and mercury lamps are

1426-401: Is a type of microdisplay that has gained popularity due to its high image quality and ability to display high-resolution images. LCos display systems typically consist of three main components: the LCos panel, the light source, and the optical system. The LCos panel is the heart of the display system. It consists of an array of pixels that are arranged in a grid pattern. Each pixel is made up of

1488-409: Is accelerated towards the anode and stabilised by the electrode shapes plus intrinsic magnetic compression generated by the current flow, and convection effects controlled by the bulb shape. Following these developments, the first successful public projection using xenon light was performed on 30 October 1950, when excerpts from a colour film ( Schwarzwaldmädel ) were shown during the 216th session of

1550-422: Is distinct from other LCD projector technologies which use transmissive LCD , allowing light to pass through the light processing unit (s). LCoS is more similar to DLP micro-mirror displays. The Hughes liquid crystal light valve (LCLV) was designed to modulate a high-intensity light beam using a weaker light source, conceptually similar to how an amplifier increases the amplitude of an electrical signal; LCLV

1612-418: Is particularly attractive as a switching mechanism in a wavelength-selective switch (WSS). LCoS-based WSS were initially developed by Australian company Engana, now part of Finisar. The LCoS can be employed to control the phase of light at each pixel to produce beam-steering where the large number of pixels allow a near continuous addressing capability. Typically, a large number of phase steps are used to create

1674-423: Is specially doped . The UV radiation released by a short-arc lamp can cause a secondary problem of ozone generation. The UV radiation strikes oxygen molecules in the air surrounding the lamp, causing them to ionize. Some of the ionized molecules then recombine as O 3 , ozone. Equipment that uses short-arc lamps as the light source must contain UV radiation shielding and prevent ozone build-up. Many lamps have

1736-534: Is starting to establish a market presence  and has been predicted to supersede the xenon arc lamp for this application. The very small size of the arc makes it possible to focus the light from the lamp with moderate precision. For this reason, xenon arc lamps of smaller sizes, down to 10 watts, are used in optics and in precision illumination for microscopes and other instruments, although in modern times they are being displaced by single mode laser diodes and white light supercontinuum lasers which can produce

1798-405: Is their viewing-angle. Thin-film transistors are usually used for constructing an active matrix so that the two terms are often interchanged, even though a thin-film transistor is just one component in an active matrix and some active-matrix designs have used other components such as diodes . Whereas a passive matrix display uses a simple conductive grid to apply a voltage to the liquid crystals in

1860-539: The German Cinematographic Society in Berlin. The technology was commercially introduced by German Osram in 1952. First produced in the 2 kW size (XBO2001), and the 1 kW (XBO1001) these lamps saw wide use in movie projection , where they replaced the older, more labor-intensive (to operate) carbon arc lamps . The white continuous light generated by the xenon arc is spectrally similar to daylight, but

1922-404: The LCoS device, a complementary metal–oxide–semiconductor (CMOS) chip controls the voltage on square reflective aluminium electrodes buried just below the chip surface, each controlling one pixel. Typical chips are approximately 1–3 cm (0.39–1.18 in) square and approximately 2 mm (0.079 in) thick, with pixel pitch as small as 2.79 μm (0.110 mils). A common voltage for all

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1984-593: The LCoS, with the beam-steering image applied on the LCOS directing the light to a particular port of the fibre array. As the wavelength channels are separated on the LCoS the switching of each wavelength is independent of all others and can be switched without interfering with the light on other channels. There are many different algorithms that can be implemented to achieve a given coupling between ports including less efficient "images" for attenuation or power splitting. WSS based on MEMS and/or liquid crystal technologies allocate

2046-411: The LCos panel. The most common light source used in LCos display systems is a high-intensity lamp. This lamp emits a broad spectrum of light that is filtered through a color wheel or other optical components to provide the necessary color gamut for the display system. The optical system is responsible for directing the light from the light source onto the LCos panel and projecting the resulting image onto

2108-414: The amplitude and/or phase of an optical pulse through a process known as Fourier-domain pulse shaping. This process requires full characterisation of the input pulse in both the time and spectral domains. As an example, an LCoS-based Programmable Optical Processor (POP) has been used to broaden a mode-locked laser output into a 20 nm supercontinuum source whilst a second such device was used to compress

2170-461: The arc. The lamps produced around 30 lumens/watt, which is about double the efficiency of the tungsten incandescent lamp, but less than more modern sources such as metal halide. They had the advantage of no mercury content, convective air cooling, no high pressure rupture risk, and nearly perfect color rendition. Due to low efficiency and competition from more common lamp types, few installations remain today, but where they do, they can be recognized by

2232-653: The availability of this noble gas, significant progress was not made until John Aldington of the British Siemens lamp company published his research in 1949. This triggered intensive efforts at the German Osram company to further develop the technology as a replacement for carbon arcs in cinema projection. The xenon lamp promised tremendous advantages of a more stable arc with less flicker, and its non-consumable electrodes allowed longer films to be shown without interruptions. Osram's primary contribution to this achievement

2294-426: The basis of higher capacity transmission systems in the future. Similarly LCoS has been used to steer light into selected cores of multicore fiber transmission systems, again as a type of Space Division Multiplexing. LCoS has been used as a filtering technique, and hence a tuning mechanism, for both semiconductor diode and fiber lasers. Active-matrix liquid-crystal display The concept of active-matrix LCDs

2356-414: The cinema ILA projectors, they were more portable, starting at 33 lb (15 kg). The early LCoS projectors had their challenges. They suffered from a phenomenon called "image sticking," where the image would remain on the screen after it was supposed to be gone. This was due to the mirrors sticking in their positions, which resulted in ghosting on the screen. However, manufacturers continued to refine

2418-419: The device; the photosensor and light-blocking layer together form a rectifying junction, producing a DC voltage bias across the liquid crystal layer, transferring the image to the reflecting side by changing the rotation of polarization in the twisted nematic liquid crystal. On the reflecting side, a high-intensity, polarized projection light source reflects selectively from the dielectric mirror based on

2480-548: The envelope fragments should breakage occur. Normally, the shield is removed once the lamp is installed in the lamp housing. When the lamp reaches the end of its useful life, the protective shield is put back on the lamp, and the spent lamp is then removed from the equipment and discarded. As lamps age, the risk of failure increases, so bulbs being replaced are at the greatest risk of explosion. Xenon short-arc lamps come in two distinct varieties: pure xenon, which contains only xenon gas; and xenon-mercury, which contains xenon gas and

2542-428: The exterior of the arc tube. The lifetime of a xenon arc lamp varies according to its design and power consumption, with a major manufacturer quoting average lifetimes ranging from 500 hours (7 kW) to 1,500 (1 kW). Interest in the xenon discharge was first aroused by P. Schulz in 1944, following his discovery of its near-continuous spectrum and high colour rendering white light. Owing to wartime limitations on

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2604-414: The high efficiency s-polarisation state of the diffraction grating. The input light from a chosen fibre of the array is reflected from the imaging mirror and then angularly dispersed by the grating which is at near Littrow incidence , reflecting the light back to the imaging optics which directs each channel to a different portion of the LCoS. The path for each wavelength is then retraced upon reflection from

2666-399: The lamp has a rather low efficacy in terms of lumens of visible light output per watt of input power. Today, almost all movie projectors in theaters employ these lamps, with power ratings ranging from 900 watts up to 12 kW. Omnimax (Imax Dome) projection systems use single xenon lamps with ratings as high as 15 kW. As of 2016, laser illumination for digital theater projectors

2728-551: The light produced radiates from a pinpoint-sized cloud of plasma near the face of the cathode. However, the plasma cloud in a xenon-mercury lamp is often smaller than that of a pure xenon lamp of equivalent size, due to the electron stream losing its energy more rapidly to the heavier mercury atoms. Xenon-mercury short-arc lamps have a bluish-white spectrum and extremely high UV output. These lamps are used primarily for UV curing applications, sterilizing objects, and generating ozone . Xenon short-arc lamps also are manufactured with

2790-509: The need for a polarizing filter, resulting in a brighter and more vibrant image. The D-ILA technology has since become a popular choice for home theater enthusiasts. LCoS projectors have continued to evolve, with manufacturers introducing features like 4K resolution and HDR ( High Dynamic Range ) support. LCoS projectors are now available at a range of price points, from affordable models for home theater use to high-end professional models used in commercial installations. LCoS display technology

2852-422: The output to 400 fs, transform-limited pulses. Passive mode-locking of fiber lasers has been demonstrated at high repetition rates, but inclusion of an LCoS-based POP allowed the phase content of the spectrum to be changed to flip the pulse train of a passively mode-locked laser from bright to dark pulses. A similar approach uses spectral shaping of optical frequency combs to create multiple pulse trains. For example,

2914-556: The pixels is supplied by a transparent conductive layer made of indium tin oxide on the cover glass. The history of LCoS projectors dates back to June 1972, when LCLV technology was first developed by scientists at Hughes Research Laboratories working on an internal research and development project. General Electric demonstrated a low-resolution LCoS display in the late 1970s. LCLV projectors were used primarily for military flight simulators due to their large and bulky size. A joint venture between Hughes Electronics and JVC (Hughes-JVC)

2976-418: The polarization within the liquid crystal being controlled by the photosensor. The dielectric mirror is formed by sputtering alternating layers of TiO 2 and SiO 2 , with the final SiO 2 layer etched to align the liquid crystal material. Later development of the LCLV used similar semiconductor materials arranged in the same basic structures. The LCLV principle is carried forward in

3038-403: The polarizing sheets and cells of liquid crystal, a matrix of thin-film transistors to make a thin-film-transistor liquid-crystal display . These devices store the electrical state of each pixel on the display while all the other pixels are being updated. This method provides a much brighter, sharper display than a passive matrix of the same size. An important specification for these displays

3100-402: The region from 850 to 900 nm. This spectral region can contain about 10% of the total emitted light. Light intensity ranges from 20,000 to 500,000 cd/cm . An example is the "XBO lamp", which is an OSRAM trade name for a pure xenon short-arc lamp. For some applications, such as endoscopy and dental technology, light guide systems are included. As in a pure xenon lamp, the majority of

3162-409: The simple concatenation of adjacent channels to create a single broader channel. LCoS-based WSS, however, permit dynamic control of channel centre frequency and bandwidth through on-the-fly modification of the pixel arrays via embedded software. The degree of control of channel parameters can be very fine-grained, with independent control of the centre frequency and either upper- or lower-band-edge of

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3224-469: The target area, an active-matrix display uses a grid of transistors and capacitors with the ability to hold a charge for a limited period of time. Because of the switching action of transistors, only the desired pixel receives a charge, and the pixel acts as a capacitor to hold the charge until the next refresh cycle, improving image quality over a passive matrix. This is a special version of a sample-and-hold circuit. Xenon arc lamp A xenon arc lamp

3286-560: The technology, and today's LCoS projectors have largely overcome this issue. Sony introduced its SXRD (Silicon X-tal Reflective Display) technology in 2004. SXRD was an evolution of LCoS technology that used even smaller pixels and a higher resolution, resulting in an even more accurate image. The SXRD technology was used in Sony's high-end home theater projectors, and it quickly gained a reputation for its exceptional picture quality. JVC introduced an updated D-ILA technology in 2006, which eliminated

3348-470: The tungsten electrodes are welded to strips of pure molybdenum metal or Invar alloy, which are then melted into the quartz to form the envelope seal. Because of the very high power levels involved, large lamps are water-cooled. In those used in IMAX projectors, the electrode bodies are made from solid Invar and tipped with thoriated tungsten. An O-ring seals the tube, so that the naked electrodes do not contact

3410-408: The two most common lamps used in wide-field fluorescence microscopes . Xenon arc lamps can be roughly divided into three categories: Each consists of a fused quartz or other heat resistant glass arc tube, with a tungsten metal electrode at each end. The glass tube is first evacuated and then re-filled with xenon gas. For xenon flashtubes, a third "trigger" electrode usually surrounds

3472-561: The use of optical filters), solar simulation for age testing of materials, rapid thermal processing, material inspection and sintering. Though not commonly known outside of Russia and the former Soviet satellite countries, long arc xenon lamps were used for general illumination of large areas such as rail stations, sports arenas, mining operations, and nuclear power plant high bay spaces. These lamps, Лампа ксеноновая ДКСТ , literally "lamp xenon DKST" were characterized by high wattages ranging from 2 kW to 100 kW. The lamps operated in

3534-428: The water. To achieve maximum efficiency, the xenon gas inside short-arc lamps is maintained at an extremely high pressure — up to 30 atmospheres (440 psi / 3040 kPa) — which poses safety concerns. If a lamp is dropped or ruptures while in service, pieces of the lamp envelope can be thrown at high speed. To mitigate this, large xenon short-arc lamps are normally shipped in protective shields, which will contain

3596-405: The water. In low power applications the electrodes are too cold for efficient electron emission and are not cooled. In high power applications an additional water cooling circuit for each electrode is necessary. To reduce cost, the water circuits are often not separated and the water needs to be deionized to make it electrically non-conductive, which lets the quartz or some laser media dissolve into

3658-620: Was founded in 1992 to develop LCLV technology for commercial movie theaters under the branding ILA (Image Light Amplifer). One example was 72.5 in (1,840 mm) tall and weighed 1,670 lb (760 kg), using a 7 kW Xenon arc lamp . In 1997, engineers at JVC developed the D-ILA (Direct-Drive Image Light Amplifier) from the Hughes LCLV, which led to smaller and more affordable digital LCoS projectors, using three-chip D-ILA devices. Although these were not as bright and had less resolution than

3720-466: Was its thorough research of xenon discharge physics, which directed its developments towards very short arcs for DC operation with a particular electrode and bulb geometry. The cathode is kept small to reach high temperatures for thermionic emission, the anode being larger to dissipate the heat generated as incoming electrons are decelerated. Most light is generated immediately in front of the cathode tip, where arc temperatures reach 10,000 °C. The plasma

3782-467: Was named after the common name for the triode vacuum tube . A high-resolution, low-intensity light source (typically a CRT ) was used to "write" an image in the CdS photosensor layer, which is energized by a transparent indium tin oxide electrode, driven by an alternating current source at approximately 10 mV. A CdTe light-blocking layer prevents the low-intensity writing light from shining through

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3844-514: Was proposed by Bernard J. Lechner at the RCA Laboratories in 1968. The first functional AMLCD with thin-film transistors was made by T. Peter Brody , Fang-Chen Luo and their team at Westinghouse Electric Corporation in 1972. However, it took years of additional research and development by others to launch successful products. The term "active matrix" was coined by T. Peter Brody in 1975. The most common type of AMLCD contains, besides

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