Multi-beam exposer unit

A multi-beam exposer unit comprising:

• M sets of light sources for emitting Ni (i=1−M) light beams;
• first optical means including a plurality of finite focal lenses for converting light beams emitted from the respective light sources to convergent light, 33 ∑ i = 1 M ⁢ ( Ni - 1 )
• first synthesizing reflection mirror for reflecting a predetermined rate of incident light and transmitting a predetermined rate of incident light so as to synthesize M groups of beams passing through the finite focal lenses, thereby combining 34 ∑ i = 1 M ⁢ Ni
• emission light from the respective finite focal lenses as one beam, M sets of optical members, having positive power with a large absolute value as compared with a case of a main scanning direction, for further converging the beam in a sub-scanning direction, and M−1 second synthesizing reflection mirror for reflecting M groups of beams from M sets of optical members to be substantially overlaid on each other in a first direction;
• deflecting means, having reflection surfaces formed to be rotatable, for deflecting light to a predetermined direction;
• second optical means two having plastic lenses for image-forming 35 ∑ i = 1 M ⁢ Ni
• beams on a predetermined image surface at an equal speed, and for correcting an inclination of the deflecting means, wherein the two plastic lenses include an image forming characteristic of one lens showing that each of the two lens is positioned such that a distance from a reflection point on the deflecting means is shorter than a distance from the an image surface, one plastic lens placed on the side of the deflecting means side has a function of moving an image forming position to the side of the deflecting means at a portion close to the center of the lens, and moving the image forming position of the scanning direction to a side opposite to the deflecting means at a portion close to the lend end portion.

A multi-beam exposer unit comprising:

• M sets of light sources for emitting one Ni (i=1−M) light beams;
• first optical means including a plurality of finite focal lenses for converting light beams emitted from the respective light sources to convergent light, 36 ∑ i = 1 M ⁢ ( Ni - 1 )
• first synthesizing reflection mirror for reflecting a predetermined rate of incident light and transmitting a predetermined rate of incident light so as to synthesize M groups of beams passing through the finite focal lenses, thereby combining 37 ∑ i = 1 M ⁢ Ni
• emission light from the respective finite focal lenses as one beam, M sets of optical members, having positive power with a large absolute value as compared with a case of a main scanning direction, for further converging the beam in a sub-scanning direction, and M−1 second synthesizing reflection mirror for reflecting M groups of beams from M sets of optical members to be substantially overlaid on each other in a first direction;
• deflecting means, having reflection surfaces formed to be rotatable, for deflecting light to a predetermined direction;
• second optical means having two plastic lenses for image-forming 38 ∑ i = 1 M ⁢ Ni
• beams on a predetermined image surface at an equal speed, and for correcting an inclination of the deflecting means, wherein each of the two plastic lenses is positioned to include an image forming characteristic showing that a distance from a reflection point on the deflecting means is shorter than a distance from the image surface, one plastic lens placed on the side of the deflecting means side has a function of moving an image forming position of a scanning direction and an image forming position of a perpendicular direction to the side of the deflecting means seeing from the image surface at a portion close to the center of the lens.

A multi-beam exposer unit comprising:

• M sets of light sources for emitting Ni (i=1−M) light beams;
• first optical means including a plurality of finite focal lenses for converting light beams emitted from the respective light sources to convergent light, 39 ∑ i = 1 M ⁢ ( Ni - 1 )
• first synthesizing reflection mirror for reflecting a predetermined rate of incident light and transmitting a predetermined rate of incident light so as to synthesize M groups of beams passing through the finite focal lenses, thereby combining 40 ∑ i = 1 M ⁢ Ni
• emission light from the respective finite focal lenses as one beam, M sets of optical members, having positive power with a large absolute value as compared with a case of a main scanning direction, for further converging the beam in a sub-scanning direction, and M−1 second synthesizing reflection mirror for reflecting M groups of beams from M sets of optical members to be substantially overlaid on each other in a first direction;
• deflecting means, having reflection surfaces formed to be rotatable, for deflecting light to a predetermined direction;
• second optical means having two plastic lenses for image-forming 41 ∑ i = 1 M
• beams on a predetermined image surface at an equal speed, and for correcting an inclination of the deflecting means, wherein each of the two plastic lenses is positioned to include an image forming characteristic showing that a distance from a reflection point on the deflecting means is shorter than a distance from the image surface, one plastic lens placed on the side of the deflecting means side has a function of moving a beam position of a scanning direction to an optical axis at a portion close to a lens end portion, and the other lens placed on the side of the image surface has a function of further moving the beam position of the scanning direction to the optical axis at a portion close to the lens end portion.