Fuji Xerox Co., Ltd.

Yoshihito Sekikawa

Takayoshi Suzuki

Tsuneo Toda

Kazuhiro Yoshino

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

The optical scanning device of the present invention which handles plural light beams reduces the number of the optical components to the minimum, and thereby intends to reduce the cost, shrink the size, and secure high performance. The optical scanning device of the present invention minimizes the number of deflectors that deflect light beams with a constant angular velocity in a direction corresponding to the main scanning direction to one, and also minimizes the number of polygon mirrors included in the deflector and the number of rotation drive units of the polygon mirror each to one. Further, the device makes up two f&thgr; lens systems for converging the light beams into a specific size and scanning the beam spots with a substantially constant speed with two pairs of the f&thgr; lenses each, and disposes the f&thgr; lens systems on the both sides of the deflector. Two light beams each fall on and go out from the f&thgr; lens systems, and the deflector performs the main scanning of these four light beams.

Optical scanning device

A light scanning device deflects a plurality of light beams by a deflecting means performs divided scanning on a single scanning line on a photoconductor with the plurality of deflected light beams. When the scanning line is scanned, a detecting means detects a light beam passing through a predetermined position in front of a position where the light beam first strikes an image forming range on the photoconductor. An oscillating means oscillates a specified number of clocks in a time interval from when the light beam is detected by the detecting means until it is detected thereby again. An adjusting means makes adjustments so as to irradiate a plurality of light beams based on clocks oscillated by the oscillating means. In a time interval after the light beam is detected by the detecting means until it is detected thereby again, a plurality of light beams are irradiated based on the specified number of clocks. Therefore, even if unevenness occurs in the deflecting speed of the deflecting means, dots can be formed at the same intervals in scanning a plurality of scanning lines. Thus, it is possible to prevent discontinuous joints occurring in each of the images formed with a plurality of light beams.

Light scanning device, optical device, and scanning method of optical device

An optical scanning device comprises a multi-faceted rotating polygon mirror for deflecting an incident beam in main scanning direction, a first light source for bringing a first beam into incidence on the polygon mirror at an angle of +.alpha. with respect to a central line connecting from a rotation center of the polygon mirror to a central position of a scanned surface, the first light source arranged such that the first beam is deflected at an angle of -2.alpha. by while the polygon mirror rotates at an angle of .alpha., a second light source for bringing a second beam into incidence on the polygon mirror at an angle of -.alpha. with respect to the central line, the second light source arranged such that the second beam is deflected at an angle of -2.alpha. by while the polygon mirror rotates at an angle of .alpha., a first reflecting mirror for scanning the scanned surface by reflecting the deflected first beam, the first reflecting mirror arranged so one end portion thereof as to cross over the central line and to avoid an unnecessary beam from reflection faces adjoining to a normal reflection face of the polygon mirror, and a second reflecting mirror for scanning the scanned surface by reflecting the deflected second beam.

Light scanning device, optical device, and scanning method of optical

An optical scanning apparatus includes: a rotational polygonal mirror, on the side of which a plurality of reflecting surfaces are provided, the reflecting surfaces deflecting a beam of incident light in the primary scanning direction at a substantially equal angular velocity; a first optical system for forming a beam of light sent from the light source into an image long in the primary scanning direction in such a manner that the formed image strides over the plurality of deflecting surfaces; and an f.theta. lens for converging the beam of light deflected on the deflecting surface at a position close to the surface of the photoreceptor drum so that a spot of light irradiated on the photoreceptor drum can be moved at a substantially equal speed. In the optical scanning apparatus, the angles .alpha. and .beta. satisfy the following expression:

Optical scanning apparatus

An optical scanning apparatus includes: a rotational polygonal mirror on the the side of which a plurality of reflecting surfaces are provided, the reflecting surfaces deflecting a beam of incident light in the primary scanning direction at a substantially equal angular velocity; a first optical system for forming a beam of light sent from the light source into an image long in the primary scanning direction in such a manner that the formed image strides over the plurality of deflecting surfaces; and an f.theta. lens for converging the beam of light deflected on the deflecting surface at a position close to the surface of the photoreceptor drum so that a spot of light irradiated on the photoreceptor drum can be moved at a substantially equal speed. In the optical scanning apparatus, the angles .alpha. and .beta. satisfy the following expression:

An optical scanning device having: a beam diameter shaping optical system which shapes a diameter of a light beam from a light source and focuses the light beam as a line image which is long in a direction corresponding to a main scanning direction; polygon mirror having a reflecting surface at one of a focusing position and a vicinity of the focusing position of the line image, the polygon mirror deflecting a light beam, which is incident on the polygon mirror, at a uniform angular speed in the direction corresponding to the main scanning direction; a cylindrical mirror disposed at a light beam reflecting side of the polygon mirror, the cylindrical mirror having power to converge a light beam in only a subscanning direction which is orthogonal to the main scanning direction, and converging a light beam on a surface-to-be-scanned; and an f .theta. lens system disposed between the polygon mirror and the cylindrical mirror, and having power to converge a light beam only in a main scanning direction, and converging a light beam, which is incident on the f .theta. lens system, onto the surface-to-be-scanned via the cylindrical mirror so that a light spot is scanned at a uniform speed. Because the f .theta. lens system only has power in the main scanning direction, a configuration of each lens of the f .theta. lens system can be made simple and compact.

Of lenses constituting an f.multidot..theta. lens, with respect to the lens L2 having a greatest difference between absolute values of surface power at both surfaces thereof, a convex surface having a greater absolute value of surface power is made to abut through line contact against columnar abutment members projecting from the optical housing 10 perpendicularly to the scanning direction. In addition, flat portions provided at both ends of the lens in the scanning direction thereof are supported by supporting members, and the lens is affixed to the abutment members and by means of leaf springs.

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Iwatsuki, Japan

Yoshihito Sekikawa