US 7,598,974 B2 · Multi-beam optical scanning device

Abstract

It is an object of the present invention to realize a multi-beam optical scanning device which is suitable for high speed and high recording density by almost completely offsetting and correcting a deviation of focusing positions in a main scanning direction of plural spots in an entire surface to be scanned without deteriorating focusing properties at all. The multi-beam optical scanning device includes: a light source device 1 having plural luminescence parts; a rotating polygon mirror 5; a first optical system 2 which converts plural light beams into convergent light beams or divergent light beams; and a third optical system 6 which guides the light beams onto a surface to be scanned 7 of a drum shape, and when it is assumed that a maximum value of a positional deviation amount generated in a first direction is δY1, a maximum value of a positional deviation amount generated in a second direction is δY2, and a maximum value of a positional deviation amount generated in a third direction is δY3, conditional expression (1) is satisfied.

A multi-beam optical scanning device comprising:

light source means which has plural luminescence parts arranged apart from each other in both a main-scanning direction and a sub-scanning direction;
a rotating polygon mirror which scans in deflection by a deflection plane plural light beams emitted from the plural luminescence parts, respectively;
an incident optical system which is arranged in an optical path leading from the light source means to the rotating polygon mirror, and converts the plural light beams into convergent light beams or divergent light beams;
and
an imaging optical system which images the plural light beams scanned in deflection by the deflection plane of the rotating polygon mirror on a surface to be scanned, the surface being formed in a drum-like shape of which a rotation axis extends along the main-scanning direction,
wherein, in a sub-scanning section, the respective light beams to be made incident on the surface to be scanned are made incident such that principal rays thereof form a finite angle with respect to a normal line of the surface to be scanned, respectively, whereby a first relative positional deviation is generated between imaging points on the surface to be scanned in a first direction in parallel with the main-scanning direction,
in a main-scanning section, the convergent light beams or divergent light beams scanned in deflection by the deflection plane of the rotating polygon mirror are made incident on the imaging optical system, whereby a second relative positional deviation is generated between imaging points on the surface to be scanned in a second direction in parallel with the main-scanning direction, and
the plural light beams emerged from the plural luminescence parts have relative differences in respective wavelengths thereof, whereby a third relative positional deviation is generated between imaging points on the surface to be scanned in a third direction in parallel with the main-scanning, and
when it is assumed that
a number of the plural luminescence parts is N,
an average value of an angle in the main scanning section formed by the principal rays of the plural light beams emitted from the incident optical system and an optical axis of the imaging optical system is γ,
a focal length in the main scanning section of the incident optical system is fcol,
an interval of the plural luminescence parts is d,
an average value of an angle in the sub-scanning section formed by the principal rays of the plural light beams incident on the surface to be scanned and the normal line of the surface to be scanned is β,
a radius of a circle inscribed in the rotating polygon mirror is r,
a maximum scanning angle of the plural light beams scanned in deflection by the rotating polygon mirror is η,
an angle formed by the normal line of the surface to be scanned in the maximum scanning position of the plural light beams which are scanned in deflection by the rotating polygon mirror in the main-scanning section, and the plural light beams is θmax,
a maximum value of the relative wavelength difference of the plural light beams emitted from the plural luminescence parts is δλ,
a distance from a light outgoing side principal plane of the imaging optical system to a natural convergent point of the convergent light beams or the divergent light beams converted by the incident optical system is Sd,
a distance from the light outgoing side principal plane of the imaging optical system to a point, in which the convergent light beams or the divergent light beams converted by the incident optical system are converged and imaged by the imaging optical system, is Sk;
an fθ coefficient of the third optical system is f, and
an interval of imaging points in the sub-scanning direction on the surface to be scanned of the plural light beams determined from a resolution is P,
the following conditional expression is satisfied:

P
⁡
(
N
-
1
)
⁢
sin
⁢
⁢
β
⁢
⁢
tan
⁢
⁢
θ
max
-
(
r
⁢
⁢
tan
⁢
η
2
⁢
d
⁡
(
N
-
1
)
2
⁢
f
col
⁢
(
cos
⁡
(
2
⁢
arctan
⁢
d
⁡
(
N
-
1
)
2
⁢
f
col
)
+
cos
⁢
⁢
γ
⁢
⁢
tan
⁢
⁢
η
)
sin
⁡
(
γ
2
+
η
2
)
⁢
Sk
Sd
+
9.5
⁢
δλ
⁢
⁢
f
)

≤
0.014
and the second direction and the third direction are directions opposite the first direction.

118 more elements

Multi-beam optical scanning device

Life of this patent

Multi-beam optical scanning device

Life of this patent

Abstract

Claims3