Method and apparatus for scan line skew correction using a gradient index electrooptic prism

A raster output scanner for providing selective skew alignment correction, comprising:

• means for generating a light beam modulated in accordance with a video input data signal;
• means for scanning the light beam onto a movable imaging surface being transported in a process direction to provide successive scan lines on the movable imaging surface;
• an optical element for selectively deflecting the light beam to correct scan line skew on the imaging surface as a function of voltage applied thereacross, including
• a member including a pair of optically transmissive plate members defining a chamber therebetween;
• a liquid crystal material substantially filling the chamber, said liquid crystal material having a variable index of refraction responsive to an electric field therethrough;
• and
• means for generating an inhomogenous electric field through said liquid crystal material to produce a refractive index gradient across said optical element.

An electrostatographic printing machine of the type in which a raster output scanner produces a modulated light beam wherein the modulated light beam is scanned across a movable photoconductive imaging surface being transported in a process direction for recording latent images thereon, comprising:

• means for generating a light beam modulated in accordance with a video input data signal;
• means for scanning the light beam onto a movable imaging surface being transported in a process direction to provide successive scan lines on the movable imaging surface;
• an optical element for selectively deflecting the light beam to correct scan line skew on the imaging surface as a function of voltage applied thereacross, including
• a member including a pair of optically transmissive plate members defining a chamber therebetween;
• a liquid crystal material substantially filling the chamber, said liquid crystal material having a variable index of refraction responsive to an electric field therethrough;
• and
• means for generating an inhomogenous electric field through said liquid crystal material to produce a refractive index gradient across said optical element.