Image formation device
AssigneeKabushiki Kaisha Toshiba
InventorsGoro Oda, Takashi Shiraishi
Life of this patent
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Abstract
An image formation device for forming an electrostatic latent image on a photosensitive body using a semiconductor laser to generate a laser beam, a collimating lens for focusing the laser beam into a parallel beam, a collimating lens unit which is rotatable and arranged to flatten the laser beam from the collimating lens, a polygonal mirror for scanning the laser beam by means of reflecting surfaces, and a first and a second scanning lens for cooperatively scanning the optical path for moving the beam from the polygonal mirror onto the photosensitive body at a constant speed.
Claims18
An image formation device for forming an electrostatic latent image on a photosensitive body by means of a laser beam comprising:
- (a) a semiconductor laser for generating a laser beam to form an electrostatic latent image on the photosensitive body;
- (b) a collimating lens for arranging the laser beam from said samiconductor laser into parallel beam;
- (c) flattening means for flattening the laser beam from said collimating lens;
- (d) scanning means for scanning by deflecting the laser beam from said flattening means in a main scanning direction, said laser beam being propogated along an optical path, said optical path having a mid-point between a surface of the photosensitive body and the scanning means;
- (e) a first and second scanning lenses for cooperatively correcting the path of the laser beam so as to move the laser beam from said scanning means on the surface of said photosensitive body at a constant speed;
- (f) said first scanning lens being arranged on the scanning means side of said mid-point;
- (g) said second scanning lens being arranged on the photosensitive body side of said mid-point;
- and
- (h) said second scanning lens having a power in the main scanning direction and a power in a sub-scanning direction which is at least several times stronger than the power in the main scanning direction.
An image formation device for forming an electrostatic latent image on a photosensitive body by means of a laser beam, comprising:
- (a) semiconductor laser for generating a laser beam to form an electrostatic latent image on the photosensitive body;
- (b) a collimating lens for arranging the laser beam from said semiconductor laser into a parallel beam;
- (c) a collimating lens unit mounted, freely turnably with the laser beam as the center, on a plane being perpendicular to the laser beam emitted from said collimating lens in order to flatten the laser beam from said collimating lens;
- (d) a polygonal mirror for deflectively scanning in a specified scanning direction by means of reflecting surfaces provided on a rotating circle in order to deflectively scan the laser beam from said collimating lens unit in a main scanning direction, said laser beam being propogated along an optical path, said optical path having a mid-point between a surface of the photosensitive body and the scanning means;
- (e) first and second scanning lenses for cooperatively scanning the optical path to move the laser beam from the polygonal mirror over said photosensitive body at a constant speed;
- (f) said first scanning lens arranged on the polygonal mirror side of said mid-point;
- and
- (g) said second scanning lens arranged on the photosensitive body side of said mid-point and having a power in the main scanning direction and a power in a sub-scanning direction that is at least several times the power in the main scanning direction, and having both an incidence surface and an emission surface;
- wherein both of the incidence and the emission surfaces of said second scanning lens are formed to be noncylindrical surfaces with power in the main scanning direction, and the power and the form of a generatrix in the sub-scanning direction of both surfaces of said second scanning lens are functions of image height in the main scanning direction;
- whereby deviation from an f.theta. characteristic due to the first scanning lens is corrected principally by the form of the generatrix of the noncylindrical surfaces having power in the main scanning direction;
- and
- bending of an image surface conjugated with a deflecting point of said polygonal mirror is corrected principally by the power and the form of the generatrix in the sub-scanning direction.
Dependencies are inferred from the claim text.