Three colour electronic raster scanner - uses digital raster signals to operate laser writing head and thus control projected image

摘要

The document is scanned in the three colours by a point-to-point scan and the separate colour densities recorded as a digital signal pattern, after passing through an analoger-to-digital converter. The digital signal allows simple modulation of the pattern for colour correction and serves to control the writing laser projected onto the copy. Different colour densities are simply reproduced by varying the spacing of the raster points so that only one type of point is used. This allows simple control of the writing laser. The screen angle may be varied to minimise the Moiree effect.