LASER PLATE MAKING APPARATUS WITH AUTOFOCUS FUNCTION AND METHOD FOR REMOVING DISTURBANCE OF AUTOFOCUS-DETECTING LASER

摘要

PROBLEM TO BE SOLVED: To smoothly perform an autofocusing function by removing disturbance at the time of plate processing by combining a low output autofocus beam with a high output laser beam, detecting a focus error from a reflected beam on a resin sheet, and focus regulating corresponding to an error amount. ;SOLUTION: An autofocus (AF) laser beam from a detecting LD 56 of an AF detecting block 16 is arrived at a plate sheet 2 via an AF drive block 14 to process it, reflected, returned via the same route, and returned to an non- polarized beam splitter(NPBS) 58 of the block 16. A part of the beam is reflected on the NPBS 58. A focus error signal and a reference signal are calculated by an astigmatism matrix circuit 44, and sent to a DSP control circuit 40. The circuit 40 calculates a focus error amount, ends a lens position movement signal to a lens driver 20 based on it to energize a moving coil 71, thereby regulating an objective lens 52 at a position of just focusing.;COPYRIGHT: (C)1998,JPO