Grating light valve: Difference between revisions

The '''grating light valve''' ('''GLV''') is a "micro projection" technology whichthat operates using a dynamically adjustable [[diffraction]] grating. It competes with other [[light valve]] technologies such as [[Digital Light Processing]] (DLP) and [[liquid crystal on silicon]] (LCoS) for implementation in [[video projector]] devices such as [[rear-projection television]]s. The use of [[microelectromechanical systems]] (MEMS) in optical applications, which is known as optical MEMS or micro-opto-electro-mechanical structures (MOEMS), has enabled the possibility to combine the mechanical, electrical, and optical components in very small tiny-scale.

Silicon Light Machines (SLM), in Sunnyvale CA, markets and licenses GLV technology with the capitalised trademarks ''"'Grated Light Valve'''" and GLV, previously Grating Light Valve.<ref>{{Cite web|quote=our patented Grated Light Valve (GLV) modules|url=http://www.siliconlight.com/htmlpgs/homeset/homeframeset.html|title=Home page|publisher=Silicon Light Machines|accessdateaccess-date=April 23, 2010|archive-url=https://web.archive.org/web/20100425041859/http://www.siliconlight.com/htmlpgs/homeset/homeframeset.html|archive-date=April 25, 2010}}</ref><ref name=sid98>{{Citationcite web |url=http://www.siliconlight.com/webpdf/sid98.pdf|title=GLV Technology: Update and Novel Applications |authorsauthor=D. T. Amm, |author2=R. W. Corrigan, |website=Silicon Light Machines, Sunnyvale, CA |workarchive-url=[[Society for Information Display]] Symposium|date=19 May 1998|location=Anaheim, CA|archiveurl=httphttps://web.archive.org/web/20040806064731/http://www.siliconlight.com/webpdf/sid98.pdf|archivedatearchive-date=2004-08-06}}</ref> The valve diffracts [[laser]] light using an array of tiny movable ribbons mounted on a silicon base. The GLV uses six ribbons as theeach pixel's [[diffraction]] gratings. forElectronic eachsignals pixel.alter Thethe alignment of the gratings is altered by electronic signals, and this displacement controls the intensity of the diffracted light in a very smooth gradation.

The light valve was originallyinitially developed at [[Stanford University]], in California, by electrical engineering professor [[David M. Bloom]], along with [[William Banyai|William C. Banyai]], Raj Apte, [[Francisco Sandejas]], and [[Olav Solgaard]], professor in the [[Stanford Department of Electrical Engineering]]. In 1994, the start-up company [[Silicon Light Machines]] was founded by Bloom to develop and commercialize the technology. Cypress Semiconductor acquired Silicon Light Machines in 2000 and sold the company to Dainippon Screen. Before the acquisition by Dainippon Screen, several marketing articles were published in EETimes, EETimes China, EETimes Taiwan, Electronica Olgi, and Fibre Systems Europe, highlighting Cypress Semiconductor's new MEMS manufacturing capabilities. The company is now wholly owned by Dainippon Screen Manufacturing Co., Ltd.<ref>[http://www.screen.co.jp/press/NR080702E.pdf Dainippon Screen Mfg. Co., Ltd.]</ref>

In July 2000, [[Sony]] announced the signing of a technology licensing agreement with SLM<ref>[http://www.sony.net/SonyInfo/News/Press_Archive/200206/02-023E/ Sony Develops a Grating Light Valve display device that gives high resolution, excellent contrast ratio and wide color reproduction]</ref><ref>[{{Cite web |url=http://meko.co.uk/glv.shtml |title=Sony Signs Technology License Agreement with SLM] |access-date=2010-02-03 |archive-url=https://web.archive.org/web/20100120030238/http://www.meko.co.uk/glv.shtml |archive-date=2010-01-20 }}</ref> for the implementation of GLV technology in laser projectors for large venues,<ref>{{cite web|url=http://www.hdtvexpert.com/pages/glv.htm|date=2005-06-23|title=SAY, ISN'T THAT ELVIS? The Grating Light Valve emerges from hiding in Salt Lake City|accessdatearchive-url=2008|archiveurl=httphttps://web.archive.org/web/20051126211347/http://www.hdtvexpert.com/pages/glv.htm|archivedatearchive-date=2005-11-26}}</ref> but by 2004 Sony announced the SRX-R110 front projector using its own LCoS-based technology [[SXRD]].

SLM then partnered with [[Evans & Sutherland]] (E&S). Using GLV technology, E&S developed the E&S Laser Projector, designed for use in domes and planetariums.<ref>[{{Cite web |url=http://www.es.com/products/digital_theater/digistar3-laser.asp |title=Digistar 3 Laser] |access-date=2009-02-03 |archive-date=2009-01-16 |archive-url=https://web.archive.org/web/20090116183836/http://www.es.com/products/digital_theater/digistar3-laser.asp }}</ref> The E&S Laser Projector was incorporated into the [[Digistar 3]] dome projection system.

The GLV device is built on a silicon [[wafer]] and consists of parallel rows of ''"'highly reflective micro-ribbons'''" – ribbons of sizes of a few µmμm with a top layer of aluminium – suspended above an air gap that areis configured such that alternate ribbons (active ribbons are interlaced with static ribbons) can be dynamically actuated. Individual electrical connections to each active ribbon electrode provide for independent actuation.

The ribbons and the substrate are electrically conductive so that the [[Electrostatic deflection (structural element)|deflection]] of the ribbon can be controlled in an analog manner: When the voltage of the active ribbons is set to ground potential, all ribbons are undeflected, and the device acts as a mirror so the incident light returns along the same path. When a voltage is applied between the ribbon and base conductor, an electrical field is generated and deflects the active ribbon downward toward the substrate. This deflection can be as big as one-quarter wavelength hence creating diffraction effects on incident light that is reflected at an angle that is different from that of the incident light. The wavelength to diffract is determined by the spatial frequency of the ribbons. As this spatial frequency is determined by the photolithographic mask used to form the GLV device in the [[CMOS]] fabrication process, the departure angles can be very accurately controlled, which is useful for optical switching applications.

The switchingSwitching from undeflected to maximum deflection of the ribbon is really fast; itdeflection can switchoccur in 20 nanoseconds, which is a million times faster than conventional [[LCD]] display devices, and about 1000 times faster than TI’sTI's [[Digital Micromirror Device|DMD]] technology. This high speed can be achieved thanks to the small size, small mass, and small excursion (of a few hundreds of nanometers), of the ribbons. Besides, there is no physical contact between moving elements which makes the lifetime of the GLV as long as 15 years without stopping (over 210 billion switching cycles).

The GLV technology has been applied to a wide range ofvarious products, from laser-based HDTV sets to computer-to-plate offset printing presses to DWDM components used for wavelength management. Applications of the GLV device in maskless photolithography have also been extensively investigated.<ref name=sid98 />

To build a display system using the GLV device, different approaches can be followed: ranging from a simple approachprocess using a single GLV device with a white light as a source, thus having a [[monochrome]] system, to a more complex solution using three different GLV devices each for one of the RGB primaries' sources that once diffracted require differentadditional optical filters to point the light onto the screen or an intermediate using a single white source with a GLV device.

Besides, the light can be diffracted by the GLV device into an eyepiece for [[virtual retinal display]], or into an optical system for image projection onto a screen ([[Video projector|projector]] and [[Rear-projection television|rear-projector]]).<ref>Teklas S. Perry. ''Tomorrow's TV'', ''[[IEEE Spectrum]]'', April 2004. </ref><ref>[{{Cite web |url=http://www.siliconlight.com/webpdf/SPIE%20Jan04%20SLM%20WrtEng%205348-5%20.pdf |title=Jahja I. Trisnadi, Clinton B. Carlisle, Robert Monteverde. ''"Overview and Applications of Grating Light Valve-based optical write engines for high-speed digital imaging''", January 26, 2004.] |access-date=February 25, 2010 |archive-url=https://web.archive.org/web/20081010015714/http://www.siliconlight.com/webpdf/SPIE%20Jan04%20SLM%20WrtEng%205348-5%20.pdf |archive-date=October 10, 2008 }}</ref><ref>[http://spie.org/x648.html?product_id=273868 David M. Bloom. ''"The Grating Light Valve: Revolutionizing Display Technology, 1995. (Silicon Light Machines)''"] SPIE Publications</ref><ref>[httphttps://wwwapps.dtic.mil/cgi-binsti/pdfs/GetTRDoc?AD=ADA412187&Location=U2&doc=GetTRDoc.pdf Francis Pickard, Celine Campillo, Keith K. Niall, Carl Larouche, Hubert Jerominek. ''"MEMS-based Light Valves for Ultra-high Resolution Projection Displays''"]</ref>

* [[Digital Light Processing|DLP]]

* [[Liquid crystal on silicon]]

* [http://www.siliconlight.com Silicon Light Machines]

* [http://www.screen.co.jp/index.html Dainippon Screen Manufacturing Co., Ltd.]

* [http://www.sony.net/SonyInfo/News/Press_Archive/200206/02-023E/ Sony]

* [http://www.es.com Evans & Sutherland]

* [https://web.archive.org/web/20080705223522/http://www.meko.co.uk/glv.shtml MEKO-European Display Data and Market Research]

* [http://www.hdtvexpert.com HDTVExpert]

* [httphttps://wwwapps.dtic.mil/cgi-binsti/pdfs/GetTRDoc?AD=ADA412187&Location=U2&doc=GetTRDoc.pdf Defence Research and Development Canada]