Fuji Xerox Co., Ltd.

Kazuhiro Yoshino

Yoshihito Sekikawa

Yoshihiro Yamamoto

Kazuhiro Sone

An image forming apparatus includes an image carrier, a rotary developer unit having a developing roll opposed to the image carrier when located at a developing position and an exposure device for writing a latent image onto the image carrier, wherein an optical path from the exposure device to the image carrier passes within a circumscribed circle of the developing roll with the center of rotation of the rotary developer unit as the center of the circle. The image carrier is located so as to provide the developing position above a horizontal line passing the center of rotation of the rotary developer unit, and the exposure device is located so as to provide a beam exit position below the horizontal line.

Image forming apparatus using an image carrier and rotary developer unit

In an optical scanning apparatus used in an image forming apparatus for scanning a plurality of optical beams on photosensitive members and for synthesizing a plurality of images formed on the photosensitive members to output a synthesized image as a single image, positional shifts occurred in the plural images can be corrected in a simple arrangement and in low cost. The optical scanning apparatus is arranged by a light source for projecting plural optical beams; deflecter for deflecting the optical beams; first beam sensor for sensing positions of the respective optical beams along an optical beam scanning direction; second beam sensor for sensing positions of the respective optical beams along a direction intersected with the scanning direction; and modulation controller for controlling a modulation of each of the plural optical beams projected from the light source based upon the sense results obtained from the first beam sensor and the second beam sensor in such a manner that a positional shift occurred when plural images formed by the respective optical beams are synthesized with each other is suppressed.

Optical scanning apparatus capable of correcting positional shifts contained in plural images to be synthesized

In a scanning optical system, a first light detecting body is disposed so as to be coplanar with a surface to be scanned, whereas a second light detecting body is disposed in front of the surface to be scanned. Outputs of the light detecting bodies are applied to a first rise time detecting circuit and a second rise time detecting circuit to detect rise times, respectively. The rise times are applied to a comparing circuit, which compares a difference therebetween to detect a displacement of a beam of light that is scanning the surface to be scanned from the focus. A control circuit outputs a signal for correcting the displacement from the focus. Simultaneously therewith, a spot judging circuit detects the profile of a spot of the beam of light that is scanning the surface to be scanned from the rise time.

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Iwatsuki, Japan

Kazuhiro Yoshino