Patent ID: 6229650
Filing Date: 2001-05-08
Classification: G02B

Abstract:
An optical imaging head for transferring an image onto a printing plate mounted on a drum surface of an internal drum platesetter or an external drum platesetter, the optical imaging head comprising:a line illumination module for generating a substantially uniform line of radiation, said line illumination module comprises a bar of laser diodes, a fast axis collimating lens for evenly dispersing radiation in a fast axis direction, and a slow axis collimating lens for evenly dispersing the radiation in a slow axis direction;a grating light valve, forming an object plane, which receives the line of radiation from the line illumination module and generates diffractive orders of modulated radiation, said grating light valve comprising (i) an addressable diffraction grating formed of moving parts on the surface of a silicon chip, and (ii) pixels of dual-supported parallel ribbons formed of silicon nitride and coated with a reflective aluminum top layer;a first lens group for receiving the modulated radiation and for adjusting image magnification independent of image focus;a second lens group for receiving and passing the magnification-adjusted modulated radiation from the first lens group to the printing plate, said second lens group adjusting image focus independent of image magnification; anda stop, placed between the first and second lens groups, having a single aperture for (i) passing zero order diffractive magnification-adjusted modulated radiation to the printing plate mounted on the drum surface of the internal drum platesetter or the external drum platesetter, and (ii) blocking non-zero order diffractive magnification-adjusted modulated radiation from incidence with the printing plate mounted on the drum surface of the internal drum platesetter or the external drum platesetter.