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US 8,797,622 B2Granted
Scanning optical apparatus
AssigneeBrother Kogyo Kabushiki Kaisha
InventorsHidetaka Hoshino, Yoshifumi Nakamura, Hitoshi Fujino
Life of this patent
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Abstract
In a scanning optical apparatus, an illumination optical system has a diffractive power φdM in a main scanning direction, a diffractive power φdS in a sub-scanning direction, a refractive power φnM in the main scanning direction, and a refractive power φnS in the sub-scanning direction. A ratio φnM/φdM in the main scanning direction for a focal length fi in a range of 10-30 mm satisfies: g2(fi)≦φnM/φdM≦g1(fi), where A(Z)=(3.532×107)Z2+3023Z+0.7010, B(Z)=(5.719×107)Z2+4169Z+0.7678, C(Z)=(1.727×107)Z2+3244Z+0.4217, D(Z)=(1.373×108)Z2+3232Z+1.224, g1(fi)=fi{D(Z)−B(Z)}/20−0.5D(Z)+1.5B(Z), g2(fi)=fi{C(Z)−D(Z)}/20−0.5C(Z)+1.5A(Z), and a ratio φnS/φdS in the sub-scanning direction satisfies: φnS/φdS<1.3.
Claims10
A scanning optical apparatus comprising:
- a light source;
- a deflector configured to deflect a beam of light from the light source in a main scanning direction;
- an illumination optical system disposed between the light source and the deflector and configured to convert the beam of light emitted from the light source into a beam of light slightly converging in the main scanning direction and focused near the deflector in a sub-scanning direction;
- and
- a scan lens configured to cause the beam of light deflected by the deflector to be focused into a dot-like image on a target surface to be scanned,
- wherein the illumination optical system has a first diffractive power if φdM in the main scanning direction and a second diffractive power φdS in the sub-scanning direction, the first and second diffractive powers being different from each other, and has a first refractive power φnM in the main scanning direction and a second refractive power φnS in the sub-scanning direction, the first and second refractive powers being different from each other,
- wherein the illumination optical system has a focal length fi [mm] in the main scanning direction, which satisfies:
- 10≦fi≦30;
- wherein a ratio mM/mS of a lateral magnification mM in the main scanning direction to a lateral magnification mS in the sub-scanning direction, of an entire optical system which includes the illumination optical system and the scan lens, satisfies:
- mM/mS≧1.2;
- wherein a holding member provided to retain a distance between the light source and the illumination optical system has a coefficient Z of linear expansion which satisfies:
- 3.0×10−5≦Z≦9.5×10−5;
- wherein a ratio φnM/φdM of the first refractive power φnM in the main scanning direction to the first diffractive power φdM in the main scanning direction satisfies:
- g2(fi)≦φnM/φdM≦g1(fi)
- where A(Z)=(3.532×107)Z2+3023Z+0.7010, B(Z)=(5.719×107)Z2+4169Z+0.7678, C(Z)=(1.727×107)Z2+3244Z+0.4217, D(Z)=(1.373×108)Z2+3232Z+1.224, g1(fi)=fi{D(Z)−B(Z)}/20−0.5D(Z)+1.5B(Z), g2(fi)=fi{C(Z)−D(Z)}/20−0.5C(Z)+1.5A(Z);
- and
- wherein a ratio φnS/φdS of the second refractive power φnS in the sub-scanning direction to the second diffractive power φdS in the sub-scanning direction satisfies:
- φnS/φdS<1.3.
15 more elements
A scanning optical apparatus comprising:
- a light source;
- a deflector configured to deflect a beam of light from the light source in a main scanning direction;
- an illumination optical system disposed between the light source and the deflector and configured to convert the beam of light emitted from the light source into a beam of light slightly converging in the main scanning direction and focused near the deflector in a sub-scanning direction;
- and
- a scan lens configured to cause the beam of light deflected by the deflector to be focused into a dot-like image on a target surface to be scanned,
- wherein the illumination optical system has a first diffractive power φdM in the main scanning direction and a second diffractive power φdS in the sub-scanning direction, the first and second diffractive powers being different from each other, and has a first refractive power φnM in the main scanning direction and a second refractive power φnS in the sub-scanning direction, the first and second refractive powers being different from each other,
- wherein the illumination optical system has a focal length fi [mm] in the main scanning direction, which satisfies:
- 10≦fi≦30;
- wherein a ratio mM/mS of a lateral magnification mM in the main scanning direction to a lateral magnification mS in the sub-scanning direction, of an entire optical system which includes the illumination optical system and the scan lens, satisfies:
- mM/mS≧1.2;
- wherein a holding member provided to retain a distance between the light source and the illumination optical system has a coefficient Z of linear expansion which satisfies:
- 3.0×10−5≦Z≦9.5×10−5;
- wherein a ratio φnM/φdM of the first refractive power φnM in the main scanning direction to the first diffractive power φdM in the main scanning direction satisfies:
- 0.67<φnM/φdM<1.46;
- and
- wherein a ratio φnS/φdS of the second refractive power φnS in the sub-scanning direction to the second diffractive power φdS in the sub-scanning direction satisfies:
- φnS/φdS<φnM/φdM.
14 more elements
Dependencies are inferred from the claim text.