Optical system for the correction of differential scanline bow
First Claim
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1. A raster output scanner for a printing apparatus, comprising:
- a multiple beam light source having at least two emitters for emitting a plurality of light beams, said emitters being separated from one another in the sagittal direction by a maximum of 25 microns;
a photoreceptor;
a movable beam reflecting device for scanning each of the plurality of light beams along the photoreceptor;
a pre-scanning optical system for collimating the plurality of light beams and providing the collimated light beam at an angle of incidence normal to an axis of rotation for said reflecting device and at a separation of at least 40 microns, said pre-scan optical system including a collimator and a field lens device immediately adjacent said movable beam reflecting device so as to be the last element in said pre-scanning optical system, wherein said field lens device has a first conjugate distance equal to the distance between the optical center of the collimator and the field lens device and a second conjugate of infinity; and
a post-scanning optical system for focusing the light beams onto the photoreceptor at a separation of at least 127 microns.
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Abstract
The present invention is an apparatus for eliminating differential scanline bow in a raster output scanner (ROS) printing system. The apparatus employs a field lens device at the output of a pre-scanning optical assembly in order to direct the laser beams toward the scanning surface, or facet, at a right angle to the scanning surface, thereby eliminating a source of scanline bow.
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Citations
16 Claims
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1. A raster output scanner for a printing apparatus, comprising:
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a multiple beam light source having at least two emitters for emitting a plurality of light beams, said emitters being separated from one another in the sagittal direction by a maximum of 25 microns; a photoreceptor; a movable beam reflecting device for scanning each of the plurality of light beams along the photoreceptor; a pre-scanning optical system for collimating the plurality of light beams and providing the collimated light beam at an angle of incidence normal to an axis of rotation for said reflecting device and at a separation of at least 40 microns, said pre-scan optical system including a collimator and a field lens device immediately adjacent said movable beam reflecting device so as to be the last element in said pre-scanning optical system, wherein said field lens device has a first conjugate distance equal to the distance between the optical center of the collimator and the field lens device and a second conjugate of infinity; and a post-scanning optical system for focusing the light beams onto the photoreceptor at a separation of at least 127 microns. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification