Method and apparatus for generating a half-tone image representation with individual groups of one or more scanning beams controlled in response to half-tone dot information and either low-or high-resolution image data

摘要

A method and apparatus for generating a representation of a half-tone image including areas of different resolution. The apparatus comprises stores (2, 26) for storing digital color data representing color density information at low and high resolution respectively. A second store (25) stores spatial data indicating the type of image data to be used at each position on a record medium (7). A third store (2') is provided for storing half-tone dot information. A group of six light modulators (10) which generate six scanning beams are arranged side-by-side. A support (8) supporting the record medium (7) to be exposed to the scanning beams is provided while drive motors (6',9') cause relative movement between the support and the scanning beam. Scanning beam control means (25,27-32) determine the position of the beams relatively to the record medium (7) in use, compare the current position with the stored spatial data and control the beam in response to the previously generated digital color data and in response to the half-tone dot information. The plurality of beams are controlled together and at a first rate in response to low resolution data and singly or in groups and at a higher, second rate in response to high resolution image data.