| 释义 |
▪ I. † raster, n.1 Obs. rare—0.
[? f. rase v.1 + -ster.]
? A barber. Only in raster-cloth, raster house (see quots.).
c1440Promp. Parv. 424/1 Rastyr howse, or schavyng howse (S. rasyr hows), barbitondium. 1483Cath. Angl. 300/1 Raster clathe, ralla. Ibid. 300/2 Raster house (A. Raser howse), barbitondium. 1500Ortus, Ralla, a raster cloth or a shauynge clothe.
▪ II. raster, n.2|ˈræstə(r)|
[a. G. raster screen, frame, f. L. rastrum rake, f. rāsum, supine of rādĕre to scrape.]
a. A usu. rectangular pattern of parallel scanning lines forming or corresponding to the display on a cathode-ray tube; also more widely, with reference to other instruments and techniques involving systematic scanning movements or patterns without the use of a cathode-ray tube. Also raster pattern, raster scan; raster-scan vb. trans., raster-scanning vbl. n. and ppl. adj.
1934Bedford & Puckle in Jrnl. Inst. Electr. Engineers LXXV. 64 The path of the spot must, so to speak, be mapped out beforehand into a suitable line raster, which is of such a size and shape as to allow the real image of the spot to explore the whole of one picture. [Note] This word, imported from the German, is used to mean a scanning field or grating. 1939Television & Short-Wave World Pract. Handbk. No. 1. vi. 54/1 The production of the series of lines, or ‘raster’ as it is generally termed, is..purely a local function of the receiver and quite independent of any reception of signals. 1940Jrnl. R. Aeronaut. Soc. XLIV. 103 It is claimed that the electron Raster microscope overcomes these difficulties. The principle of the microscope is as follows:—A thin electron beam is made to scan the object in a ‘Raster’ as in television. 1946Jrnl. Inst. Electr. Engineers XCIII. iiia. 1560/2 A raster approximately an inch square was then substituted for the noise pattern, obtained by applying the output from two saw-tooth oscillators, one of 50 c/s and the other of 10 kc/s, to the two pairs of plates of the tube. 1952Electronic Engin. XXIV. 166/1 If a raster composed of horizontal scanning lines is further divided into the appropriate number of vertical lines, each line will become broken up into dots. 1966[see interlace v. 6]. 1968P. R. Thornton Scanning Electron Microscopy i. 8 Three years later [in 1938] v. Ardenne..built the first scanning electron microscope which used two magnetic lenses to provide a small electron spot at the specimen. Two sets of magnetic coils were used to scan the beam across the specimen in a television-like raster. 1969Barton & Ward Handbk. Radar Measurement viii. 227 Raster-scanning pencil beams. These radars can be analyzed as search radars or sequential-processing trackers in both angular coordinates. 1970New Scientist 4 June (Suppl.) 7/2 The screen can be ‘raster-scanned’ as on a TV screen (i.e. the light is deflected across the screen in a series of lines gradually moving to the bottom). 1973Sci. Amer. Oct. 73/1 The spectroheliograms were made by holding the diffraction grating at one angle, so that only a single wavelength fell on the photomultiplier. The solar image was then scanned in a raster pattern to build up a picture of the sun in that one wavelength. 1973Physics Bull. May 275/1 A flying spot performs a raster scan of the whole picture and with the help of a photodetector transforms the entire optical information—spots and all—into the memory of a large online computer. 1977Sci. Amer. Oct. 84/2 In a circular-scan radar system the raster of the cathode-ray tube rotates synchronously with the antenna.
b. Cinemat. and Photogr. A fine grid, comprising wires, slits, or lenticular elements, placed in front of the projection screen in some stereoscopic cinematography systems, notably that invented by F. Savoye in 1942. Also raster screen.
1952E. F. Linssen Stereo-Photogr. in Practice xxi. 291 In 1945 B. T. Ivanov wrote on ‘raster-stereoscopy in the cinema’. Ibid. 292 Savoye's Cyclostereoscopic system... The cone allows the two beams to pass through many slits.. with which it is provided, and these same slits (constituting a revolving grid or raster) also act as selectors for the spectators. 1957K. C. M. Symons Stereo Photogr. 205 Another method depends on the provision of a grid or raster screen in front of the projection screen. This method, which has a certain affinity with the parallax stereogram..forms the basis of two methods of projection, one Russian, the other French. Ibid. 213 Raster, a term used to describe certain autostereoscopic methods which depend on the use of a screen for multiplying and selecting the images. 1958Newnes Compl. Amat. Photogr. 235 An alternative method of projection is the Cyclosterscopic system... This system consists of a metal cone of fine grids or rasters which revolves around the screen and is not noticeable in motion. 1965Focal Encycl. Photogr. (rev. ed.) II. 1207/1 Raster screens consist of an arrangement of vertical wires interposed between the screen surface and the audience... There are also patented screens in which the projection surface is composed of vertical lenticular prisms, or of spherical lenticular elements graduated in size.
Hence as v. trans., to scan (an area) with a beam that goes over it in a raster pattern; ˈrastered ppl. a., (of a beam) made to scan an area thus.
1975Nature 9 Oct. 521/1 Methods by which the properties of inorganic materials may be measured quantitatively using the interaction of a rastered kilovolt electron beam with a solid. 1978Ibid. 3 Aug. 457/2 Fig. 1 shows..two X-ray maps obtained (using electron microprobe X-ray fluorescence) by rastering the same region with a 30-kV electron beam and collecting in sequence the K Kα and Ca Kα rays. |