Wobulation
Encyclopedia
Wobulation is a term which refers to the known variation (or wobble) in a characteristic. Examples of where the term is used, include to describe advanced radar waveform modulations - where the repetition rate or centre frequency of a signal is changed in a repetitive fashion to reduce the probability of detection.
In large-screen television technology
, wobulation is Hewlett-Packard
's term for a form of interlacing designed for use with fixed pixel display
s. The term is loosely derived from the word 'wobble' and was inspired by HP's work with the overlap of printing ink. Wobulation reduces the cost and complexity of components required for the creation of high resolution TVs.
Wobulation works by overlapping pixel
s. It does so by generating multiple sub-frames of data while an optical image shifting mechanism (e.g. the mirror of a digital micromirror device
) then displaces the projected image of each sub-frame by a fraction of a pixel (e.g. one-half or one-third). The sub-frames are then projected in rapid succession, and appear to the human eye as if they are being projected simultaneously and superimposed. For example, a high-resolution HDTV video frame is divided into two sub-frames, A and B. Sub-frame A is projected, and then the miniature mirror on a digital micromirror device switches and displaces sub-frame B one half pixel length as it is projected. When projected in rapid succession, the sub-frames superimpose, and create to the human eye a complete and seamless image. If the video sub-frames are aligned so that the corners of the pixels in the second sub-frame are projected at the centers of the first, the illusion of double the resolution is achieved, like in an interlaced CRT
display. Thus a lower resolution fixed pixel device using wobulation can emulate the picture of higher resolution fixed device, at a reduced cost.
, wobulation is used only to double the horizontal resolution of a display, unlike CRT interlacing that doubles the vertical resolution. However, wobulation is capable of doubling the vertical and horizontal resolution of an image (2x wobulation).
While wobulation can in theory be used in many types of display devices, it is currently primarily used in displays using Digital Light Processing (DLP). DLP is a Texas Instruments
(TI) technology which relies on a Digital Micromirror Device (DMD) chip. TI calls its implementation of wobulation 'SmoothPicture'. Horizontal wobulation used in current TI products allows a DMD chip with a 960×1080 mirror array to produce a 1920×1080 pixel picture; most recent designs employed in 3D DLP sets use "offset-diamond pixel layout", where the mirrors form a "checkerboard
pattern" array. Also, the image overlap inherent in the use of wobulation eliminates the 'screen door' effect common on other fixed pixel displays such as plasma
and LCD, but may in some implementations also create some reduction in sharpness. Wobulation is used by a number of TV manufacturers, including Hewlett-Packard
, Mitsubishi
, RCA
, Samsung
, and Toshiba
.
Wobulation technology used in TVs is becoming obsolete, as manufacturers shift away from producing rear projection TVs.
In large-screen television technology
Large-screen television technology
Large-screen television technology developed rapidly in the late 1990s and 2000s. Various thin screen technologies are being developed, but only the liquid crystal display , plasma display and Digital Light Processing were released on the public market...
, wobulation is Hewlett-Packard
Hewlett-Packard
Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...
's term for a form of interlacing designed for use with fixed pixel display
Fixed pixel display
Fixed pixel displays are display technologies such as LCD and plasma that use an unfluctuating matrix of pixels with a set number of pixels in each row and column...
s. The term is loosely derived from the word 'wobble' and was inspired by HP's work with the overlap of printing ink. Wobulation reduces the cost and complexity of components required for the creation of high resolution TVs.
Wobulation works by overlapping pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
s. It does so by generating multiple sub-frames of data while an optical image shifting mechanism (e.g. the mirror of a digital micromirror device
Digital micromirror device
A digital micromirror device, or DMD, is an optical semiconductor that is the core of DLP projection technology, and was invented by Dr. Larry Hornbeck and Dr. William E. "Ed" Nelson of Texas Instruments in 1987....
) then displaces the projected image of each sub-frame by a fraction of a pixel (e.g. one-half or one-third). The sub-frames are then projected in rapid succession, and appear to the human eye as if they are being projected simultaneously and superimposed. For example, a high-resolution HDTV video frame is divided into two sub-frames, A and B. Sub-frame A is projected, and then the miniature mirror on a digital micromirror device switches and displaces sub-frame B one half pixel length as it is projected. When projected in rapid succession, the sub-frames superimpose, and create to the human eye a complete and seamless image. If the video sub-frames are aligned so that the corners of the pixels in the second sub-frame are projected at the centers of the first, the illusion of double the resolution is achieved, like in an interlaced CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
display. Thus a lower resolution fixed pixel device using wobulation can emulate the picture of higher resolution fixed device, at a reduced cost.
, wobulation is used only to double the horizontal resolution of a display, unlike CRT interlacing that doubles the vertical resolution. However, wobulation is capable of doubling the vertical and horizontal resolution of an image (2x wobulation).
While wobulation can in theory be used in many types of display devices, it is currently primarily used in displays using Digital Light Processing (DLP). DLP is a Texas Instruments
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
(TI) technology which relies on a Digital Micromirror Device (DMD) chip. TI calls its implementation of wobulation 'SmoothPicture'. Horizontal wobulation used in current TI products allows a DMD chip with a 960×1080 mirror array to produce a 1920×1080 pixel picture; most recent designs employed in 3D DLP sets use "offset-diamond pixel layout", where the mirrors form a "checkerboard
Checkerboard
A checkerboard or chequerboard is a board of chequered pattern on which English draughts is played. It is an 8×8 board and the 64 squares are of alternating dark and light color, often red and black....
pattern" array. Also, the image overlap inherent in the use of wobulation eliminates the 'screen door' effect common on other fixed pixel displays such as plasma
Plasma display
A plasma display panel is a type of flat panel display common to large TV displays or larger. They are called "plasma" displays because the technology utilizes small cells containing electrically charged ionized gases, or what are in essence chambers more commonly known as fluorescent...
and LCD, but may in some implementations also create some reduction in sharpness. Wobulation is used by a number of TV manufacturers, including Hewlett-Packard
Hewlett-Packard
Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...
, Mitsubishi
Mitsubishi
The Mitsubishi Group , Mitsubishi Group of Companies, or Mitsubishi Companies is a Japanese multinational conglomerate company that consists of a range of autonomous businesses which share the Mitsubishi brand, trademark and legacy...
, RCA
RCA
RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
, Samsung
Samsung
The Samsung Group is a South Korean multinational conglomerate corporation headquartered in Samsung Town, Seoul, South Korea...
, and Toshiba
Toshiba
is a multinational electronics and electrical equipment corporation headquartered in Tokyo, Japan. It is a diversified manufacturer and marketer of electrical products, spanning information & communications equipment and systems, Internet-based solutions and services, electronic components and...
.
Wobulation technology used in TVs is becoming obsolete, as manufacturers shift away from producing rear projection TVs.
External links
- Hewlett-Packard Wobulation
- Explanation at Popular SciencePopular SciencePopular Science is an American monthly magazine founded in 1872 carrying articles for the general reader on science and technology subjects. Popular Science has won over 58 awards, including the ASME awards for its journalistic excellence in both 2003 and 2004...