Patent ID: 6396646
Filing Date: 2002-05-28
Classification: G02B,G03F

Abstract:
A multi-beam optical system, comprising:a light source that emits a light beam; a beam-dividing element that divides the light beam emitted by said light source into a plurality of light beams which emanate therefrom at different angles, respectively; a propagation optical system through which the divided light beams propagate, said propagation optical system including a plurality of curved surface mirrors; and an image-forming optical system that forms a plurality of beam spots on an objective surface by converging the light beams propagated through said propagation optical system, wherein said propagation optical system is configured to substantially satisfy a condition represented by an equation: &Sum;i=1n&it;Ai&it;Î¸i&it;Ï‰0Ï‰l=0,wherein, i represents a mirror number of said plurality of curved surface mirrors counted along a direction where the divided light beams propagate, n represents the number of said plurality of curved surface mirrors, &thgr;i represents an inclination angle of an optical axis of an i-th curved surface mirror with respect to a central axis of a rectilinearly proceeding beam which would not be deflected by said beam-dividing optical element and proceed rectilinearly, Ai represents a coefficient for an i-th curved surface mirror, Ai being +1 when a particular beam of said divided light beams is on one side with respect to a central axis of said rectilinearly proceeding beam, Ai being âˆ’1 when the particular beam of said divided light beams is on the other side with respect to the central axis of said rectilinearly proceeding beam, &ohgr;0 is a diameter of the particular beam emerged from said beam-dividing optical element, and &ohgr;i represents a diameter of the particular beam at said i-th curved surface mirror.