picture tube

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picture tube

[′pik·chər ‚tüb]
(electronics)
A cathode-ray tube used in television receivers to produce an image by varying the electron-beam intensity as the beam is deflected from side to side and up and down to scan a raster on the fluorescent screen at the large end of the tube. Also known as kinescope; television picture tube.

Picture tube

A cathode-ray tube used as a television picture tube. Television picture tubes use large glass envelopes that have a light-emitting layer of luminescent material deposited on the inner face. A modulated stream of high-velocity electrons scans this luminescent layer in a series of horizontal lines so that the picture elements (light and dark areas) are recreated.

In a color picture tube (see illustration), the glass bulb is made in two pieces, the face panel and the funnel-neck region. The separate face panel allows the fabrication of the segmented phosphor screen and the mounting of the shadow mask. The two glass pieces are sealed together by a special frit to provide a strong vacuum-tight seal.

The light-emitting colored phosphors on the segmented screen can be either in dot arrays or, now more commonly, in line arrays. Typically, the trios of vertical phosphor lines are spaced 0.6– 0.8 mm apart. Most tubes use a black matrix screen in which the phosphor lines are separated by opaque black lines. This black matrix reduces reflected light, thereby giving better contrast, and also provides a tolerance for the registration of the electron beam with the phosphor lines.

The shadow mask is made of a thin (0.10–0.17 mm) steel sheet in which elongated slits (one row of slits for each phosphor-line trio) have been photoetched. It is formed to a contour similar to that of the glass panel and is mounted at a precise distance from the glass. The width of the slits and their relative position to the phosphor lines are such that the electron beam from one of the three electron guns can strike only one of the sets of color phosphor lines. The shadow mask “shadows” the beam from the other two sets of phosphor lines.

The electron gun for color is similar to that for monochrome except that there are three guns, usually arranged side by side, or in-line. This triple gun has common structural elements, but uses three independent cathodes with separate beam forming and focusing for each beam.

The electromagnetic deflection yoke deflects or bends the beams, as in a monochrome tube, to scan the screen in a television raster. In addition, the yoke's magnetic field is shaped so that the three beams will be deflected in such a way that they land at the same phosphor trio on the screen at the same time. This convergence of the beams produces three images, one in red, one in green, and one in blue, that are superimposed to give a full-color picture. See Cathode-ray tube, Television

References in periodicals archive ?
A delegation led by executives of Shenzhen China Star is said to visit Chunghwa Picture Tubes in the coming days to begin talks with the latter's chairman and president on the stake-buying issue.
To fill that data gap, his team tested 36 picture tubes produced between 1984 and 1998.
We have been disadvantaged in this growing market environment because we have to buy our 32-inch and 35-inch picture tubes from competitors.
With tablet PCs quickly emerging as hot-sellers, the partnership will facilitate PVI's plan to cash in on the fast-growing market, with institutional investors saying the firm can secure additional capacity of e-paper displays and FFS (finger field switching) panels from Chunghwa Picture Tubes by buying its convertible bonds for only NT$1.
These sizes are being added to a product line that covers 19V through 35V picture tubes.
being a system integrator, adding that the investment bank Credit Suisse will invest in the money-losing Chunghwa Picture Tubes Inc.
has reported plans to expand production of color TV picture tubes, install new automated production processes and start up a new production line for projection TV picture tubes.
The display market continues to demand high-brightness, low-power panels, and we're pleased that another industry leader such as Chunghwa Picture Tubes chooses to enable this using PenTile RGBW technology," said Joel Pollack, Clairvoyante president and chief executive officer.
to explore the market for small and medium-sized display panels, Chunghwa Picture Tubes Ltd.
Serving primarily the North American market, the state-of- the-art facility will manufacture very large screen (31-inch and larger) picture tubes for Thomson as well as for other television manufacturers.
Leading Asian suppliers include Hitachi, Sharp, Sanyo Electric and NEC of Japan; Samsung Electronics and LG Electronics of South Korea; and AU Optronics, Chi Mei Optoelectronics and Chunghwa Picture Tubes of Taiwan.