Patent ID: 7522324
Filing Date: 2009-04-21
Classification: G02B

Abstract:
1. An optical scanning device, comprising: light source means; deflecting means having a deflecting surface; an input optical system configured to direct a light beam emitted from said light source means onto said deflecting means; an imaging optical system configured to image a light beam scanningly deflected by the deflecting surface of said deflecting means upon a surface to be scanned, said imaging optical system having at least one imaging optical element of transmission type; and at least one reflection type optical element having a reflecting surface and being disposed at an optical path between said imaging optical element of transmission type and said surface to be scanned; wherein said imaging optical element of transmission type has first to fourth transmission surfaces and is configured so that the light beam scanningly deflected by the deflecting surface of said deflecting means passes through said imaging optical element of transmission type in an order from the first transmission surface to the second transmission surface, and that, after being reflected by the reflecting surface of said reflection type optical element, the light beam subsequently passes again through said imaging optical element of transmission type in an order from the third transmission surface to the fourth transmission surface, wherein the transmission surface of said at least one imaging optical element through which the light beam passes again has an axial combined power ø within a main-scan section, while the reflecting surface of said at least one reflection type optical element has an axial combined power øM within a main-scan section of the reflecting surface, which axial combined powers satisfy a relation and, wherein the axial combined power within a main-scan section of the transmission surface of said imaging optical element through which the light beam passes again is comprised of combined powers of four optical surfaces which include the first transmission surface on which the light beam scanningly deflected by the deflecting surface of said deflecting means is incident, the second transmission surface on which the light beam passed through the first transmission surface is incident, the third transmission surface on which the light beam reflected by the reflecting surface of said reflection type optical element is incident, and the fourth transmission surface on which the light beam passed through the third transmission surface is incident.