SU1283704A1 - Method of producing raster picture - Google Patents

Abstract

The invention relates to printing and improves the quality of the raster image and reduces the cost of its production. To do this, a half-tone image is exposed to the film through two gray contact rasters with an irregular structure or two lines of gray contact raster with an optical density interval of ADt 1.0 and uDg 1, 0-1.8 with partial exposures from the main exposure for each raster, amounting to 100%. During exposure, ruled rasters are arranged so that their lines form an angle of from 10 to 90 ° when applied. tab. (L

Description

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This invention relates to printing, in particular, to methods for producing a raster image on photographic films for the subsequent manufacture of offset and letterpress printing forms.

The aim of the invention is to improve the quality of the raster image and reduce the cost of its production.

The drawing shows the dependence of the interval of optical densities of a halftone image on the fraction of exposure when using rasters with intervals of optical densities ADi 0.7 and uDg 1.2.

The essence of the method is that sequentially expose a half-tone image to a film through two gray contact rasters with an irregular structure or two linear gray contact rasters with optical density intervals AD, i 1.0 and ADj "1.0-1.8 sec. partial exposures, from the main exposure for each raster, amounting to 100%. During exposure, ruled rasters are arranged in such a way that their lines form an angle of from 10 dr 90 ° (when the angle is less than 10 °, noticeable moire distortions appear).

The method of exposing a halftone image onto a film sequentially through two gray rasters with an irregular structure or two line rasters makes it possible to adjust the interval of optical densities of the halftone image reproduced by the raster image by changing the fraction of exposure times through each raster used, depending on the angle between the raster images lines using raster rasters, you can get different forms of raster points - square, rhombic , round, elliptical, which contributes to the improvement of the quality of the bitmap image and the gradation transfer of the reproduced original.

The use of two rasters with a dotted structure or more than two ruled rasters is not always possible due to the occurrence of moire.

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Example 1. In contact copy-. A rotal machine on a photographic, FT41 film is exposed to a halftone image of the original, made on a transparent basis, successively through two gray contact rasters. The raster purity is 24 lin / cm, the angle of the raster lines is equal to 90. The first plant has an interval of optical densities for the FT41 film in the FT-2 DV converter, 0.7, and the second DV2 1.2. Intervals are defined within changes in the relative areas of the pastra elements from

5 5 to 90% on a raster image. The exposure time with each raster is a fraction of the main exposure of the raster. Change the magnitude of the shares behind each raster

0, provided that the sum remains equal to 100% of the exposure, the entire set of possible optical density intervals of the reproduced images of the originals from 0.7 to 1.2 is obtained.

The experimental data obtained are presented in the table, and the drawing shows the dependence of the interval of optical densities of the halftone original on the raster image on the fraction of the exposure.

If it is necessary to obtain a bitmap image of the original with a density interval of 1.1, then the fraction

The exposure for each raster is determined by the dependence of the optical density interval on the fractions, the exposure for each raster, which is given in the drawing. For the specified value

40 densities get 20% of the main exposure for the raster with an interval of 0.7, and 80% for a raster with an interval of 1.2 (shown in the drawing by the dotted line).

45 Example 2. In the photo-reproduction apparatus, on the FT41 photoplay, a halftone image of the original made on an opaque base through two gray ones is sequentially exposed.

SP Contact raster with irregular structure. The first raster has a range of reproducible optical densities on the FT41 film in the FT-2 U.DI 0.65 film, the second 55 g is 1.8.

Changing the amount of exposure for each raster (as in Example 1), provided that the sum of the exposures is 100%, the whole set is obtained.

reproducible optical density ranges from 0.65 to 1.8.

The exposure time as a fraction of the main exposure for each raster is determined as in Example 1, depending on the interval of optical densities of the reproduced halftone original.

Claims (1)

Invention Formula A method of making a raster image, comprising exposing the photographic material through a contact raster-halftone image with Two partial exposures amounting to 100% of the exposure, differing TBM, which, in order to improve the quality of the raster image and reduce the cost of its production, partial exposures make two gray contact rasters with density intervals .4Di 1.0 and D 2  1.0-1.8, and as gray contact rasters, rasters with an irregular structure or two ruled rasters with a spreading angle relative to each other from 10 90 D of the optical original reproduced on the raster image in the range of 5-95% of raster elements GI I j1 I 1.2 ten 0.8iba O / fffO2 / 7S SO / Sff 76 / fS LR / HJ yffC / 7ff3tJUl / u with jopc / rr / ftr VNIIPI Order 7437/45 Circulation 421 fffO / ff fy.T Subscription Random polygons pr-tie, Uzhgorod, Project, 4 0.78 0.90 0.98 1.2 fffO / ff fy.T Subscription