Interferometric modulator display
Encyclopedia
Interferometric modulator display (IMOD, mirasol) is a technology used in electronic visual display
s that can create various colors via interference of reflected light. The color is selected with an electrically switched light modulator comprising a microscopic cavity
that is switched on and off using driver integrated circuit
s similar to those used to address liquid crystal display
s (LCD). An IMOD-based reflective flat panel display includes hundreds of thousands of individual IMOD elements each a microelectromechanical systems
(MEMS)-based device.
In one state an IMOD subpixel reflects light at a specific wavelength, while in a second state it absorbs incident light and appears black to the viewer, using a diffraction grating
effect. When not being addressed, an IMOD display consumes very little power. Unlike conventional back-lit liquid crystal displays, it is clearly visible in bright ambient light
such as sunlight. IMOD prototypes as of mid-2010 could emit 15 frames per second (fps), and in November 2011 Qualcomm
demonstrated another prototype reaching 30 fps, suitable for video playback.
wings. While a simple etalon consists of two half-silvered mirrors, an IMOD comprises a reflective membrane which can move in relation to a semitransparent thin film stack. With an air gap defined within this cavity, the IMOD behaves like an optically resonant structure whose reflected color is determined by the size of the airgap. Application of a voltage to the IMOD creates electrostatic forces which bring the membrane into contact with the thin film stack. When this happens the behavior of the IMOD changes to that of an induced absorber. The consequence is that almost all incident light is absorbed and no colors are reflected. It is this binary operation that is the basis for the IMOD's application in reflective flat panel displays. Since the display utilizes light from ambient sources, the display's brightness increases in high ambient environments (i.e. sunlight). In contrast, a back-lit LCD display suffers from incident light.
For a practical RGB color model
(RGB) display, a single RGB pixel is built from several subpixels, because the brightness of a monochromatic pixel is not adjusted. A monochromatic
array of subpixels represents different brightness levels for each color, and for each pixel, there are three such arrays: red, green and blue.
has allowed commercialization of the technology under the trademark name "mirasol", and this energy-efficient, biomimetic
technology sees application and use in portable electronics such as e-book reader
s and mobile phone
s.
IMOD displays are now available in the commercial marketplace. QMT's displays, using IMOD technology, are found in the Acoustic Research ARWH1 Stereo Bluetooth
headset device, the Showcare Monitoring system (Korea
), the Hisense
C108, and mp3 applications from Freestyle Audio and Skullcandy
. In the mobile phone marketplace, Taiwanese manufacturers Inventec
and Cal-Comp have announced phones with mirasol displays, and LG claims to be developing 'one or more' handsets using mirasol technology. These products all have only two-color (black plus one other) "bi-chromic" displays.
Electronic visual display
An electronic visual display is display technology which incorporates flat panel displays, performs as a video display, output device for presentation of images transmitted electronically, for visual reception, without producing a permanent record....
s that can create various colors via interference of reflected light. The color is selected with an electrically switched light modulator comprising a microscopic cavity
Micromachinery
Micromachines are mechanical objects that are fabricated in the same general manner as integrated circuits. They are generally considered to be between 100 nanometres to 100 micrometres in size, though that is debatable. The applications of micromachines include accelerometers that detect when a...
that is switched on and off using driver integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
s similar to those used to address liquid crystal display
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....
s (LCD). An IMOD-based reflective flat panel display includes hundreds of thousands of individual IMOD elements each a microelectromechanical systems
Microelectromechanical systems
Microelectromechanical systems is the technology of very small mechanical devices driven by electricity; it merges at the nano-scale into nanoelectromechanical systems and nanotechnology...
(MEMS)-based device.
In one state an IMOD subpixel reflects light at a specific wavelength, while in a second state it absorbs incident light and appears black to the viewer, using a diffraction grating
Diffraction grating
In optics, a diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions. The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as...
effect. When not being addressed, an IMOD display consumes very little power. Unlike conventional back-lit liquid crystal displays, it is clearly visible in bright ambient light
Available light
In photography and cinematography, available light or ambient light refers to any source of light that is not explicitly supplied by the photographer for the purpose of taking photos. The term usually refers to sources of light that are already available naturally or artificial light already being...
such as sunlight. IMOD prototypes as of mid-2010 could emit 15 frames per second (fps), and in November 2011 Qualcomm
Qualcomm
Qualcomm is an American global telecommunication corporation that designs, manufactures and markets digital wireless telecommunications products and services based on its code division multiple access technology and other technologies. Headquartered in San Diego, CA, USA...
demonstrated another prototype reaching 30 fps, suitable for video playback.
Working principle
A pixel in an IMOD-based display consists of one or more subpixels that are individual microscopic interferometric cavities similar in operation to Fabry–Pérot interferometers (etalons), and the scales in butterflyButterfly
A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured...
wings. While a simple etalon consists of two half-silvered mirrors, an IMOD comprises a reflective membrane which can move in relation to a semitransparent thin film stack. With an air gap defined within this cavity, the IMOD behaves like an optically resonant structure whose reflected color is determined by the size of the airgap. Application of a voltage to the IMOD creates electrostatic forces which bring the membrane into contact with the thin film stack. When this happens the behavior of the IMOD changes to that of an induced absorber. The consequence is that almost all incident light is absorbed and no colors are reflected. It is this binary operation that is the basis for the IMOD's application in reflective flat panel displays. Since the display utilizes light from ambient sources, the display's brightness increases in high ambient environments (i.e. sunlight). In contrast, a back-lit LCD display suffers from incident light.
For a practical RGB color model
RGB color model
The RGB color model is an additive color model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors...
(RGB) display, a single RGB pixel is built from several subpixels, because the brightness of a monochromatic pixel is not adjusted. A monochromatic
Monochrome
Monochrome describes paintings, drawings, design, or photographs in one color or shades of one color. A monochromatic object or image has colors in shades of limited colors or hues. Images using only shades of grey are called grayscale or black-and-white...
array of subpixels represents different brightness levels for each color, and for each pixel, there are three such arrays: red, green and blue.
Development
The IMOD technology was invented by Mark W. Miles, a MEMS researcher and founder of Etalon, Inc., and (co-founder) of Iridigm Display Corporation. Qualcomm took over the development of this technology after its acquisition of Iridigm in 2004, and subsequently formed Qualcomm MEMS Technologies (QMT). QualcommQualcomm
Qualcomm is an American global telecommunication corporation that designs, manufactures and markets digital wireless telecommunications products and services based on its code division multiple access technology and other technologies. Headquartered in San Diego, CA, USA...
has allowed commercialization of the technology under the trademark name "mirasol", and this energy-efficient, biomimetic
Bionics
Bionics is the application of biological methods and systems found in nature to the study and design of engineering systems and modern technology.The word bionic was coined by Jack E...
technology sees application and use in portable electronics such as e-book reader
E-book reader
An e-book reader, also called an e-book device or e-reader, is a mobile electronic device that is designed primarily for the purpose of reading digital e-books and periodicals....
s and mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s.
Commercial uses
Future IMOD panels manufacturers include, Qualcomm in conjunction with Foxlink, having established a joint-venture with Sollink (高強光電) in 2009 with a future facility dedicated to manufacturing IMOD panels. Production for this began in Jan 2011, with the fabricated panels intended for devices such as e-readers.IMOD displays are now available in the commercial marketplace. QMT's displays, using IMOD technology, are found in the Acoustic Research ARWH1 Stereo Bluetooth
Bluetooth
Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances from fixed and mobile devices, creating personal area networks with high levels of security...
headset device, the Showcare Monitoring system (Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
), the Hisense
Hisense
Hisense is a multinational electronics manufacturer based in China. It is a state-owned enterprise with publicly traded subsidiaries.The Hisense Group comprises two publicly traded companies, Hisense Electric Co Ltd, listed on the Shanghai stock exchange and Hisense Kelon Electrical Holdings Co...
C108, and mp3 applications from Freestyle Audio and Skullcandy
Skullcandy
Skullcandy is a Park City, Utah-based company that markets headphones, earphones, hands free devices, audio backpacks, MP3 players and other products. The company was founded in 2003....
. In the mobile phone marketplace, Taiwanese manufacturers Inventec
Inventec
Inventec Corporation is a Taiwan-based Original Design Manufacturer making notebook computers, servers and mobile devices. Originally established in 1975 to develop and manufacture electronic calculators, the company has since grown significantly to become one of the world's top computer...
and Cal-Comp have announced phones with mirasol displays, and LG claims to be developing 'one or more' handsets using mirasol technology. These products all have only two-color (black plus one other) "bi-chromic" displays.