US7538925B2 - Optical Scanner Including a Lens Surface That Does Not Have a Curvature in the Sub-Scanning Direction and a Line Describing This Surface in the Sub-Scanning Direction Has a Tilt Which Varies Depending on a Location of the Line in the Main Scanning Direction, the Tilt of the Line Defining an Angle Which Is Measured with Respect to the Sub-Scanning Direction, and an Image Forming Apparatus Including the Lens | Patent Bear