Method of coalescing laser beams

Abstract

A method of coalescing two or more laser beams employs an optical merging element such as a polarization beam splitter to make the laser beams substantially merged into a single laser beam of multiplied power. In the merged laser beam, however, the original laser beams cannot easily be perfectly aligned with each other. In order to have the laser beams perfectly mingled or coalesced at the position where they are focused on an object to be processed or an original to be read out or a recording medium, the original laser beams substantially merged into a single laser beam are collimated so that the collimated laser beams may be directed to the same focusing position on the object. To collimate the original laser beams in the merged beam, a part of the merged beam is split out and passed through a converging lens to cause the original laser beams focused to points on a pinhole plate by use of a converging lens, and the directions of the original laser beams are corrected to make the laser beams focused to the same point on the pinhole plate or coincide with the pinhole. By making these laser beams coincide with the pinhole, these laser beams are consequently collimated so that they can be focused to the same point on said object, whereby the laser beams are coalesced in effect.