Time-multiplexed optical shutter

Last updated

Time multiplexed optical shutter (TMOS) is a flat panel display technology developed, patented and commercialized by Uni-Pixel Displays, Inc. TMOS is based on the principles of total internal reflection (TIR), frustration of TIR (FTIR) and field sequential colour generation (FSC). This combination of features make it suitable for applications such as mobile phones, televisions and signalling systems. [1] [2] [3]



A TMOS display system consists of a group of sub-systems

A TMOS unit is arranged as a set of layers placed atop another in the following order: the light guide, a transparent conductive layer, a TFT structure and the Opcuity active layer which includes a conductive layer.

Operating principle

  1. The illumination system emits periodically red, green and blue light, each colour cycles for an equal period of time in a very high frequency.
  2. The coloured light enters inside de guide light, the mirrored edges cause a continual TIR reflections producing a highly uniform of light energy within the light guide.
  3. The light is trapped in the light guide until a voltage differential is created between the two conductive layers of the capacitor at any pixel area. When it happens the two conductive planes attract each other via Coulomb attraction.
  4. The Opcuity active layer is the only moving part of TMOS and it is pulled down until it touches the light guide. Then, the specific pixel is activated and the light escaped through it due to the phenomenon frustration of total internal reflection (FTIR).
  5. When the voltage differential disappears, the active layer returns to its initial position and the light is trapped again in the light guide.

When the two conductive layers are in contact is said that the pixel is open or active (ON), when the layers are separated then the pixel is closed or inactive (OFF) . The duration of the charge determines the amount of time the shutter is open or closed. To generate images displays, the previous process is specific for each pixel. The color generation is based on the field sequential colour (FSC) system.

Colour generation

Traditional displays use three part pixel, each pixel is created by displaying different intensities of three dots (red, blue and green) so close together that the human eye perceives them as a single colour. This technique takes advantage of the spatial additive colour. However, TMOS technology is based on temporal additive colour, it exploits the temporal resolving power of the human visual system. Red, green and blue light bursts are emitted at sufficiently high frequency that the human eye only perceive a single colours. Different durations of each burst, create different colours.

In TMOS the emitting duration of each burst is the same for the three colors, but the amount of time that each pixel stays open or closed can be only a percentage of the total time controlled by the quantity of the TFT charge (amount of time that the active layer is in contact with the light guide). Therefore, each coloured pixel is generated combining the precise time that each pixel is kept open for each colour burst.

Depending on the combination, a million of colours can be created. For instance:

To get white the pixel remains open the 100% of the total time for each burst and for black each pixel is closed the entire time.:To produce grey, the pixel should be active half of the total time for each burst (when the three values of the three components are equal, a grey is produced)
To create red, the pixel must be closed during blue and green burst, the percentage of the red cycle the pixel is open determines the shade of red.

General features


TMOS technology offers many advantages over other popular technologies like LCD, plasma and OLED.

Simplicity: The simple TMOS structure brings most of the others advantages. The five layers of an LCD become only one in TMOS. This involves a simpler manufacturing process and increases the performance.
Energy efficiency: TMOS is ten times more efficient than an LCD. In LCD less than 5–10% of the energy input is transmitted as light output, while in TMOS 61% percent of the energy is transmitted. Low power consumption makes TMOS ideal for battery-powered applications.
Low cost: Because of the TMOS simple structure the manufacturing process becomes simpler and the total cost lower. TMOS devices can be 60% cheaper than the others.
Good contrast and brightness: TMOS display systems produce 10% more brilliant images and with a better contrast ratio (4500:1) comparing with LCD (2500:1) and others (700:1)
Mean time between failures: TMOS life could achieve 300,000 hours, overcoming the 10,000 hours of OLED, 30,000 of plasma displays, 40,000 hours of CTRS and the 100,000 hours of LCD.
Scalability: Scale flexibility is another important characteristic. TMOS is the first technology capable of supporting different configurations and sizes up to 110″. Until now, OLED achieved 20″, LCD 54″ and plasma 72″.
Variety of applications: Traditional displays have specific applications: OLED for mobiles, plasma for television and LCD for computers. Thanks to scalability, TMOS will be suitable for mobile, television and computers displays.


The main disadvantage is the necessity of a very high velocity; if it is insufficient a rainbow effect could appear at blink.

Future developments

In the future, it aims to improve efficiency and features of that kind of screens. Some of these improvements are going to be a new guide light material, polycarbonate or flexible polymer, and the enlargement of the LED's gamut. What is more, the TFTs structure is going to be eliminated and a system of a stripes (rows and columns) called Simple Matrix will provide individual pixel control.

The following features are being investigated for TMOS displays:

Flexibility, allowing radius of curvature up to 20 times the displays thickness. This characteristic will enable the creation of photo-realistic images, the development of "home theatres" that surround the viewer like IMAX screens.
Readability in bright sunlight so they could be used for road and highway signs, tradeshows...etc.
Transparency, displays could have a transparent rear therefore, they could be used as windows from the inside and as displays from the outside.

Related Research Articles

Computer monitor Computer output device

A computer monitor is an output device that displays information in pictorial or text form. A monitor usually comprises a visual display, some circuitry, a casing, and a power supply. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD) with LED backlighting having replaced cold-cathode fluorescent lamp (CCFL) backlighting. Previous monitors used a cathode ray tube (CRT) and some Plasma displays. Monitors are connected to the computer via VGA, Digital Visual Interface (DVI), HDMI, DisplayPort, USB-C, low-voltage differential signaling (LVDS) or other proprietary connectors and signals.

Liquid-crystal display Display that uses the light-modulating properties of liquid crystals

A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly, instead using a backlight or reflector to produce images in color or monochrome. LCDs are available to display arbitrary images or fixed images with low information content, which can be displayed or hidden. For instance: preset words, digits, and seven-segment displays, as in a digital clock, are all good examples of devices with these displays. They use the same basic technology, except that arbitrary images are made from a matrix of small pixels, while other displays have larger elements. LCDs can either be normally on (positive) or off (negative), depending on the polarizer arrangement. For example, a character positive LCD with a backlight will have black lettering on a background that is the color of the backlight, and a character negative LCD will have a black background with the letters being of the same color as the backlight. Optical filters are added to white on blue LCDs to give them their characteristic appearance.

A plasma display panel (PDP) is a type of flat panel display that uses small cells containing plasma: ionized gas that responds to electric fields. Plasma televisions were the first large flat panel displays to be released to the public.

An active-matrix liquid-crystal display (AMLCD) is a type of flat-panel display, the only viable technology for high-resolution TVs, computer monitors, notebook computers, tablet computers and smartphones with an LCD screen, due to low weight, very good image quality, wide color gamut and response time.

OLED Diode that emits light from an organic compound

An organic light-emitting diode, also known as organic electroluminescentdiode, is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light in response to an electric current. This organic layer is situated between two electrodes; typically, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors, and portable systems such as smartphones and handheld game consoles. A major area of research is the development of white OLED devices for use in solid-state lighting applications.

A flat-panel display (FPD) is an electronic display device used to enable people to see content in a range of entertainment, consumer electronics, personal computer, and mobile devices, and many types of medical, transportation and industrial equipment. Such panels, or screens, are far lighter and thinner than traditional cathode ray tube (CRT) television sets and are usually less than 10 centimetres (3.9 in) thick. Flat-panel displays can be divided into two display device categories: volatile and static. Volatile displays require that pixels be periodically electronically refreshed to retain their state. A volatile display only shows an image when it has battery or AC mains power. Static flat-panel displays rely on materials whose color states are bistable, and as such, flat-panel displays retain the text or images on the screen even when the power is off. As of 2016, flat-panel displays have almost completely replaced old CRT displays. In many 2010-era applications, specifically small portable devices such as laptops, mobile phones, smartphones, digital cameras, camcorders, point-and-shoot cameras, and pocket video cameras, any display disadvantages of flat-panels are made up for by portability advantages.

Active matrix is a type of addressing scheme used in flat panel displays. In this method of switching individual elements (pixels), each pixel is attached to a transistor and capacitor actively maintaining the pixel state while other pixels are being addressed, in contrast with the older passive matrix technology in which each pixel must maintain its state passively, without being driven by circuitry.

Television set Device for viewing computers screen and shows broadcast through satellites or cables

A television set or television receiver, more commonly called the television, TV, TV set, tube, telly, or tele, is a device that combines a tuner, display, and loudspeakers, for the purpose of viewing and hearing television broadcasting through satellites or cables, or using it as a computer monitor. Introduced in the late 1920s in mechanical form, television sets became a popular consumer product after World War II in electronic form, using cathode ray tube (CRT) technology. The addition of color to broadcast television after 1953 further increased the popularity of television sets in the 1960s, and an outdoor antenna became a common feature of suburban homes. The ubiquitous television set became the display device for the first recorded media in the 1970s, such as Betamax, VHS and later DVD. It has been used as a display device since the first generation of home computers and dedicated video game consoles in the 1980s. By the early 2010s, flat-panel television incorporating liquid-crystal display (LCD) technology, especially LED-backlit LCD technology, largely replaced CRT and other display technologies. Modern flat panel TVs are typically capable of high-definition display and can also play content from a USB device.

LCD television Television set with liquid-crystal display

Liquid-crystal-display televisions are television sets that use liquid-crystal displays to produce images. They are, by far, the most widely produced and sold television display type. LCD TVs are thin and light, but have some disadvantages compared to other display types such as high power consumption, poorer contrast ratio, and inferior color gamut.

Backlight Form of illumination used in liquid crystal displays

A backlight is a form of illumination used in liquid crystal displays (LCDs). As LCDs do not produce light by themselves—unlike, for example, cathode ray tube (CRT) displays—they need illumination to produce a visible image. Backlights illuminate the LCD from the side or back of the display panel, unlike frontlights, which are placed in front of the LCD. Backlights are used in small displays to increase readability in low light conditions such as in wristwatches, and are used in smart phones, computer displays and LCD televisions to produce light in a manner similar to a CRT display. A review of some early backlighting schemes for LCDs is given in a report Engineering and Technology History by Peter J. Wild.

A thin-film-transistor liquid-crystal display is a variant of a liquid-crystal display that uses thin-film-transistor technology to improve image qualities such as addressability and contrast. A TFT LCD is an active matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven LCDs with a few segments.

Screen burn-in Disfigurement of a CRT, plasma or OLED display

Screen burn-in, image burn-in, or ghost image is a discoloration of areas on an electronic display such as a cathode ray tube (CRT) display or an old computer monitor or television set caused by cumulative non-uniform use of the pixels.

Electroluminescent display

Electroluminescent Displays (ELDs) are a type of flat panel display created by sandwiching a layer of electroluminescent material such as GaAs between two layers of conductors. When current flows, the layer of material emits radiation in the form of visible light. Electroluminescence (EL) is an optical and electrical phenomenon where a material emits light in response to an electric current passed through it, or to a strong electric field. The term "electroluminescent display" describes displays that use neither LED nor OLED devices, that instead use traditional electroluminescent materials. Beneq is the only manufacturer of TFEL and TAESL displays, which are branded as LUMINEQ Displays. The structure of a TFEL is similar to that of a passive matrix LCD or OLED display, and TAESL displays are essentially transparent TEFL displays with transparent electrodes. TAESL displays can have a transparency of 80%. Both TEFL and TAESL displays use chip-on-glass technology, which mounts the display driver IC directly on one of the edges of the display. TAESL displays can be embedded onto glass sheets. Unlike LCDs, TFELs are much more rugged and can operate at temperatures from −60 to 105 °C and unlike OLEDs, TFELs can operate for 100,000 hours without considerable burn-in, only losing about 80% of its initial brightness. The electroluminescent material is deposited using atomic layer deposition, which is a process that deposits one 1-atom thick layer at a time.

Thick-film dielectric electroluminescent (TDEL) technology is a phosphor-based flat panel display technology developed by Canadian company iFire Technology Corp. TDEL is based on inorganic electroluminescent (IEL) technology and has a novel structure that combines both thick- and thin-film processes. An IEL device generates light by applying an alternating electrical field to inorganic light-emitting phosphors. Traditional IEL displays are bright, very fast in video response time and highly tolerant of environmental extremes. However, the lack of full-color capability and large-size scalability has limited their application for the mainstream consumer television market. iFire has addressed these limitations by replacing the thin-film dielectric of traditional IEL technology with its patented thick-film, high-K dielectric material and structure. The result is a unique flat panel display technology that provides iFire displays with high performance and low cost potential. iFire was unable to develop displays competitive with LCD, plasma and OLED devices and wound up research and development in 2007.

Large-screen television technology Technology rapidly developed in the late 1990s and 2000s

Large-screen television technology developed rapidly in the late 1990s and 2000s. Prior to the development of thin-screen technologies, rear-projection television was used for many larger displays, and jumbotron, a non-projection video display technology, was used at stadiums and concerts. Various thin-screen technologies are being developed, but only liquid crystal display (LCD), plasma display (PDP) and Digital Light Processing (DLP) have been released on the public market. However, recently released technologies like organic light-emitting diode (OLED), and not-yet-released technologies like surface-conduction electron-emitter display (SED) or field emission display (FED), are on their way to replacing the first flat-screen technologies in picture quality.

AMOLED Display technology for use in mobile devices and televisions

AMOLED is a type of OLED display device technology. OLED describes a specific type of thin-film-display technology in which organic compounds form the electroluminescent material, and active matrix refers to the technology behind the addressing of pixels.

Electrically operated display devices have developed from electromechanical systems for display of text, up to all-electronic devices capable of full-motion 3D color graphic displays. Electromagnetic devices, using a solenoid coil to control a visible flag or flap, were the earliest type, and were used for text displays such as stock market prices and arrival/departure display times. The cathode ray tube was the workhorse of text and video display technology for several decades until being displaced by plasma, liquid crystal (LCD), and solid-state devices such as thin-film transistors (TFTs), LEDs and OLEDs. With the advent of metal-oxide-semiconductor field-effect transistors (MOSFETs), integrated circuit (IC) chips, microprocessors, and microelectronic devices, many more individual picture elements ("pixels") could be incorporated into one display device, allowing graphic displays and video.

Quantum dot display Type of display device

A quantum dot display is a display device that uses quantum dots (QD), semiconductor nanocrystals which can produce pure monochromatic red, green, and blue light.

A see-through display or transparent display is an electronic display that allows the user to see what is shown on the screen while still being able to see through it. The main applications of this type of display are in head-up displays, augmented reality systems, digital signage, and general large-scale spatial light modulation. They should be distinguished from image-combination systems which achieve visually similar effects by optically combining multiple images in the field of view. Transparent displays embed the active matrix of the display in the field of view, which generally allows them to be more compact than combination-based systems.

Low-temperature polycrystalline silicon (LTPS) is polycrystalline silicon that has been synthesized at relatively low temperatures compared to in traditional methods. LTPS is important for display industries, since the use of large glass panels prohibits exposure to deformative high temperatures. More specifically, the use of polycrystalline silicon in thin-film transistors (LTPS-TFT) has high potential for large-scale production of electronic devices like flat panel LCD displays or image sensors.


  1. Larry F. Hodges, "Time-Multiplexed Stereoscopic Computer Graphics," IEEE Computer Graphics March/April 1992 (vol. 12 no. 2) pp. 20-30 DOI Bookmark:
  2. Achintya K. Bhowmik; Zili Li; Philip J. Bos (31 July 2008). Mobile Displays: Technology and Applications. John Wiley & Sons. pp. 281–. ISBN   978-0-470-99463-4.
  3. IEEE Computer Society
  1. Web of Unipixel