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  Optical multi-beam scanning device and image forming apparatusUSPTO Application #: 20070296802Title: Optical multi-beam scanning device and image forming apparatus Abstract: An optical multi-beam scanning device has a plurality of pre-deflection optical units, an optical path synthesizing member and an excessive light processing member. The excessive light processing member processes excessive light emitted from an excessive light emitting surface with is not an incident surface nor an emitting surface of the optical path synthesizing member. The excessive light processing member has a multi-stage taper constitution with a plurality of taper surfaces having different tilt angles. (end of abstract) Agent: Foley And Lardner LLP Suite 500 - Washington, DC, US Inventor: Yasushi Kuribayashi USPTO Applicaton #: 20070296802 - Class: 347243000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070296802. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application is a divisional based upon U.S. application Ser. No. 10/820,750, filed Apr. 9, 2004, incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION [0002] The invention relates to an image forming apparatus such as a copying machine, a printer, and a composite machine which has a copying function and a printing function, and an optical multi-beam scanning device which is mounted on the image forming apparatus. Specifically, the invention relates to the optical multi-beam scanning device and the image forming apparatus for a color mode. [0003] Image forming apparatuses mainly adopt a method in which a number of light beams to be scanned at a time is increased (multi-beam) as speed heightening means of writing optical systems. In writing optical systems of four-tandem (one pass) color composite machines, it becomes mainstream that a polygon mirror, a scanning lens, and the like are shared in order to reduce the cost. [0004] In the case where the adoption of multi-beam is considered, a method of synthesizing laser beams from individual LDs (laser diodes) with one another using a beam splitter, a half mirror and the like so as to lead the synthesized laser beam to a polygon mirror, and a method of leading a plurality of laser beams to a polygon mirror using an LD array for emitting the laser beams to one direction are considered. From a viewpoint of an installation space, the LD array is advantageous, but when a number of scanning light beams increases to 4, 8, . . . , synthesization using the beam splitter should be used at the same time. In the four-tandem (1 pass) color composite machines, light beams (laser beams) should be separated by a mirror so as to go to photosensitive drums for respective color components after deflection. Since separation intervals are too narrow in the method using the LD array, the method using the individual LDs is preferable. [0005] There are a lot of optical multi-beam scanning devices which adopt the method of synthesizing laser beams from the LDs using the beam splitter, the half mirror, and the like so as to lead the synthesized laser beam to the polygon mirror. [0006] Optical parts for switching a ratio of reflection and transmission by a deflecting direction of a beam from the beam splitter, the half mirror and the like or by the thickness of a reflecting layer, are applied to a synthesizing unit for optical paths of the laser beams. Even in this case, a laser beam (excessive light), which moves to a direction (for example, a reflecting direction) other than an intended direction (for example, a transmitting direction), is also present, and this laser beam becomes stray light and it might deteriorate the performance of the apparatus. [0007] A technique relating to an optical pickup is disclosed in Japanese Unexamined Patent Application Publication No. 5-54421. In this publication, a taper portion of 45.degree. is provided on a portion for housing optical parts of the optical pickup, and excessive light emitted from a polarized light beam splitter is reflected by the taper portion (an optical path of the excessive light is folded by 90.degree.) so as to let it go to the outside. There is also described that if the taper portion is painted black, it is more effective. [0008] Such a stray light countermeasure against the application of the optical parts such as the beam splitter and the half mirror can be applied only to the case where rear positions of stray light emitting surfaces of the optical parts have a sufficient space. In the optical multi-beam scanning device which leads a plurality of laser beams from a plurality of LDs to one polygon mirror, since installation positions of the respective optical parts are close to one another, the above method cannot be applied in most cases from the viewpoint of the space. SUMMARY OF THE INVENTION [0009] It is an object of the present invention to provide an optical multi-beam scanning device which is capable of preventing a bad effect on light sources and other optical parts due to stray light of light beams from an excessive light emitting surface of an optical path synthesizing optical part provided in order to guide a plurality of light beams to one deflecting surface even when a rear position of the excessive light emitting surface does not have a sufficient space, and an image forming apparatus which adopts such an optical multi-beam scanning device. [0010] An optical multi-beam scanning device of the present invention includes: a plurality of light sources; pre-deflection optical units for giving a predetermined property to light beams from the light sources, the pre-deflection optical units corresponding to the light sources, respectively; an optical path synthesizing member for aligning optical paths of the light beams from all or some of the light sources in a horizontal scanning direction after the pre-deflection optical units give the predetermined properties to the light beams or while giving them to the light beams; an excessive light processing member having a multi-stage taper constitution with a plurality of taper surfaces having different tilt angles for reflecting excessive light emitted from an excessive light emitting surface which is not an incident surface nor an emitting surface of the optical path synthesizing member; and a light deflecting device for deflecting the light beams from the pre-deflection optical units corresponding to the light sources to the horizontal scanning direction due to reflection from one surface. [0011] Further, an optical multi-beam scanning device of another aspect if the present invention includes: a plurality of light sources; pre-deflection optical units for giving a predetermined property to light beams from the light sources, the pre-deflection optical units corresponding to the light sources, respectively; an optical path synthesizing member for aligning optical paths of the light beams from all or some of the light sources in a horizontal scanning direction after the pre-deflection optical units give the predetermined properties to the light beams or while giving them to the light beams; an excessive light processing member having an absorbing surface roughly parallel with an excessive light emitting surface for absorbing excessive light emitted from the excessive light emitting surface which is not an incident surface nor an emitting surface of the optical path synthesizing member; and a light deflecting device for deflecting the light beams from the pre-deflection optical units corresponding to the light sources to the horizontal scanning direction due to reflection from one surface. [0012] The absorbing surface of the excessive light processing member is formed by adhering a light absorbing sheet to the absorbing surface, or repeating convexo-concave patterns for reflecting and absorbing the excessive light. [0013] An optical multi-beam scanning device of still another aspect of the present invention includes: a plurality of light sources; pre-deflection optical units for giving a predetermined property to light beams from the light sources, the pre-deflection optical units corresponding to the light sources, respectively; an optical path synthesizing member for aligning optical paths of the light beams from all or some of the light sources in a horizontal scanning direction after the pre-deflection optical units give the predetermined properties to the light beams or while giving them to the light beams; an excessive light processing member having repeated local patterns for dispersing excessive light emitted from an excessive light emitting surface which is not an incident surface nor an emitting surface of the optical path synthesizing member; and a light deflecting device for deflecting the light beams from the pre-deflection optical units corresponding to the light sources to the horizontal scanning direction due to reflection from one surface. [0014] An image forming apparatus of the present invention has an optical multi-beam scanning device having a plurality of light sources, a control unit for controlling light emitting timing of the light sources, and photoreceptors on which latent images are formed based on light beams from the optical multi-beam scanning device. The image forming apparatus adopts the above-mentioned optical multi-beam scanning devices as the optical multi-beam scanning device. BRIEF DESCRIPTION OF THE DRAWINGS [0015] FIG. 1 is a schematic sectional view illustrating a color image forming apparatus according to a first embodiment of the present invention; [0016] FIG. 2 is a schematic sectional view illustrating components of a post-deflection optical system in an optical multi-beam scanning device according to the first embodiment; [0017] FIG. 3 is a schematic plan view illustrating components of the optical multi-beam scanning device according to the first embodiment; [0018] FIG. 4 is an explanatory diagram illustrating an arrangement of the components of the pre-deflection optical system in the optical multi-beam scanning device according to the first embodiment in which an optical path is a linear optical path; [0019] FIGS. 5A to 5C are diagrams explaining incident light and emitted light to an optical path synthesizing optical part in the optical multi-beam scanning device according to the first embodiment; [0020] FIG. 6 is a diagram explaining excessive light from the optical path synthesizing optical part; Continue reading... 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