METHOD AND DEVICE FOR MULTI-STAGE PIXEL DENSITY SEQUENTIAL EXPOSURE OF MACHINE PLATE FOR PRINTING

摘要

PROBLEM TO BE SOLVED: To form and record images for printing which have multiple pixel density values on a machine plate for printing and to sequentially record the high-density image and low-density image at a high speed. SOLUTION: This machine plate exposing device for printing which records image information in a band shape to a band width of multiple pixels by irradiating the surface of the machine plate 4 for printing with multiple light beams through an exposure lens is equipped with a high-density exposure lens 24bH with short focal length which forms a high-density image band, a low-density exposure lens 24bL with long focal length which is arranged without interfering with the high-density exposure lens 24bH and forms a low-density image band, and electronic masks ML and MH for specific image areas which perform on/off control over the individual light beams so as to make the number of light beams made incident on the low-density exposure lens 24bL smaller than that of light beams made incident on the high-density exposure lens 24bH, and can record the high-density image and low-density image on the machine plate 4 for printing at the same time.