JP3619672B2 - Multi-beam scanning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-beam scanning device. The present invention can be used for an optical scanning device in a digital copying apparatus, a facsimile, or a laser printer.
[0002]
[Prior art]
In general, an optical scanning apparatus widely known in connection with a digital copying apparatus or the like generally couples a light source with a first optical system, and transmits a beam from the first optical system in the main scanning direction (bending of the optical path from the light source to the scanned surface). Is ignored, and the direction corresponding to the main scanning direction on the surface to be scanned is the same as the sub-scanning direction). The deflected beam is deflected by a deflector having a reflecting surface, and the deflected beam by the deflector is condensed on the scanned surface by the third optical system to scan the scanned surface.
Recently, with the aim of speeding up optical scanning, a multi-beam scanning apparatus that simultaneously scans a surface to be scanned with a plurality of beams has been intended.
Multiple beam scanning devices use multiple light sources, but in order to condense multiple beams from these multiple light sources close to each other on the scanned surface, multiple beams are combined using a beam combining component that uses polarized light. It has been proposed (for example, JP-A-8-304722).
On the other hand, multi-beam scanning is possible without using expensive beam combining parts using polarized light, and multiple beams are opened in the deflection rotation plane (a plane perpendicular to the rotation axis of the deflection reflection plane). There has been proposed a multi-beam scanning device having an angle (angle formed by projection of each beam when the plurality of beams are projected onto a deflection rotation surface) (Japanese Patent Laid-Open No. 9-146024).
However, in this case, using a “deflector whose deflection reflecting surface and its rotation axis are separated from each other by a certain distance”, a plurality of beams having an opening angle can be used for “sag amount (linear condensing portion of each beam and deflection reflection). The amount of sag is different for each beam in order to obtain good optical characteristics (beam spot diameter, constant velocity, etc.) for all beams. An optical design based on the fact that they are different is necessary.
[0003]
[Problems to be solved by the invention]
The present invention can scan the surface to be scanned with a plurality of beams without using an expensive beam combining component using polarized light, and can improve the optical characteristics such as the beam spot diameter and constant velocity for all the beams. The objective is to realize a multi-beam scanning device that can handle high speed and high image quality.
[0004]
[Means for Solving the Problems]
The multi-beam scanning device of the present invention includes a plurality of light sources, a plurality of first optical systems, a second optical system, a deflector, and a third optical system.
[0005]
The “plurality of light sources” individually emit beams for optical scanning. A semiconductor laser (LD) is suitable as these light sources.
The “first optical system” couples the plurality of light sources. The first optical system is provided according to each light source. The coupled beam may be a “parallel beam” or a “weakly convergent beam or a weakly divergent beam”.
The “second optical system” is an optical system that condenses the beam from each first optical system in a substantially linear shape that is long in the main scanning direction, and a cylinder lens or a concave cylinder mirror can be preferably used. The second optical system may be provided for each beam from each light source, that is, the same number as the light sources, but may be provided in common for a plurality of light sources.
The “deflector” has a deflecting reflection surface in the vicinity of the substantially linear condensing unit, and deflects a plurality of beams from the second optical system at an equiangular velocity, but the deflection reflecting surface and its rotation axis are at a constant distance. is seperated. That is, the deflector is used in common for each beam from a plurality of light sources, and the beams from the plurality of light sources are deflected by a common deflection reflection surface. As such a deflector, a rotary polygon mirror or a rotary dihedral mirror can be suitably used, but a “rotary single mirror” having a deflecting reflection surface and a rotation axis thereof separated from each other can also be used.
The “third optical system” includes a scanning imaging element that collects a plurality of deflected beams deflected by the deflector toward the surface to be scanned and scans the surface to be scanned at substantially constant speed.
The third optical system can include an optical element such as a folding mirror that bends the optical path of the deflected beam.
The “scanning imaging optical system” can be constituted by one or more lenses or one or more imaging mirrors, and can also be constituted as a composite system of one or more lenses and one or more imaging mirrors.
The plurality of beams from the second optical system are directed to the deflection reflection surface from the same side in the main scanning direction outside the scanning imaging element, and at least two of the plurality of beams from the second optical system are deflection rotation surfaces. Has an opening angle inside. The “open angle” refers to an “angle that allows each beam to open from the deflection reflection surface side toward the second optical system side” in the “state in which the two beams are projected into the deflection rotation surface”.
[0006]
In the above-described configuration, “when the principal rays of the plurality of deflected beams by the deflector are orthogonal to the scanning lines on the surface to be scanned, the principal rays are used as reference lines, and at least one scanning optical of the third optical system is used. The optical axis of the element can be arranged so as to be shifted to the beam side toward the deflecting reflection surface in the main scanning direction when viewed from all the reference lines . If the principal ray of an arbitrary beam deflected by the deflector is directly guided to the scanned surface without being refracted by the scanning imaging optical system, the “reference line” is the scanning line (the beam) on the scanned surface. The principal ray in a state that will be orthogonal to the scanning line) is fixed in the device space, and is generally different for each beam, and the projections into the deflection rotation plane are parallel to each other.
In this case , at least one scanning optical element of the third optical system can be provided with being tilted (referred to as being tilted with respect to the reference line in the deflection rotation plane) with respect to the reference line . That is, the scanning imaging optical system can undergo shift and tilt. Both shift and tilt are effective means for recovering the performance degradation due to the sag of the scanning imaging optical system.
The multi-beam scanning device according to claim 1 has the following characteristics.
That is, the sub-scanning direction image formation position at both the most peripheral image heights of one of the beams from the plurality of light sources (refers to the amount of field curvature in the sub-scanning direction at both the most peripheral image heights, and so on) ) Is S1 (+), S1 (-), and S2 (+), S2 (-) are the sub-scanning direction imaging positions at the two most peripheral image heights of the beam from one light source other than the above. Is the condition:
(1) (S1 (+)-S1 (-)) x (S2 (+)-S2 (-)) <0
Satisfied.
The multi-beam scanning device according to claim 2 has the following characteristics.
That is, the main scanning direction imaging position at both the most peripheral image heights of one of the beams from the plurality of light sources (refers to the amount of field curvature in the main scanning direction at both the most peripheral image heights; the same applies hereinafter). , M1 (+), M1 (-), and M2 (+), M2 (-) as the main scanning direction imaging positions at the two most peripheral image heights of the beam from one light source other than the above. :
(2) (M1 (+)-M1 (-)) x (M2 (+)-M2 (-)) <0
Satisfied.
The multi-beam scanning device according to claim 3 has the following characteristics.
That is, M1 (+) and M1 (-) are the main scanning direction imaging positions at both the most peripheral image heights of one of the beams from the plurality of light sources, and S1 (+) is the sub-scanning imaging position. , S1 (-), M2 (+), M2 (-) at the most peripheral image height of the beam from one light source other than the above, M2 (-), and S2 (+) , S2 (-), these are the conditions:
(1) (S1 (+)-S1 (-)) x (S2 (+)-S2 (-)) <0
(2) (M1 (+)-M1 (-)) x (M2 (+)-M2 (-)) <0
Satisfy both.
The multi-beam scanning device according to claim 4 is the multi-beam scanning device according to any one of claims 1 to 3 , wherein at least two beams intersect after the deflection surface when projected into the deflection rotation surface. It is characterized by that.
Even when the shift and tilt are not performed, the above condition (1) is obtained by making the refracting surface and the reflecting surface of the scanning imaging element asymmetric with respect to the optical axis in the main scanning direction and / or the sub-scanning direction. And / or (2) may be satisfied.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the embodiment shown in FIG. 1, the beams emitted from the LD1 and LD2 which are “a plurality of light sources” are coupled by the coupling lenses 3 and 4 forming the “first optical system”, respectively. Each of the cylinder lenses 5 and 6 forming the “optical system” forms an image in a substantially linear shape in the vicinity of the deflecting reflection surface 7 and extending in the main scanning direction.
Both of the two beams are reflected by the common deflecting / reflecting surface 7 of the same deflector and deflected at an equal angular velocity, and the scanned surface 20 is scanned by the scanning lenses 11 and 12 forming the “scanning imaging optical system of the third optical system”. A beam is imaged in the vicinity, and the scanned surface 20 is scanned at a substantially constant speed by a beam spot formed on the scanned surface 20. Each beam spot forms a predetermined interval in the sub-scanning direction on the surface to be scanned. Accordingly, two scanning lines separated by the interval are scanned simultaneously. At this time, the two beams emitted from the cylinder lenses 5 and 6 as the second optical system have an opening angle γ within the deflection rotation surface (a surface parallel to the drawing of FIG. 1), and the deflection reflection surface 7 of the deflector. And its rotating shaft 7A are separated by a certain distance.
[0008]
【Example】
Specific examples relating to the above embodiment will be described.
[0009]
Example 1
In the configuration shown in FIG. 1, beams emitted from LD1 and LD2 are referred to as beam 1 and beam 2, respectively. The angle formed by the beam 1 and the reference line L1 (the line when the principal ray of the beam 1 is orthogonal to the scanning line on the scanned surface 20) is 60 degrees, and the beam 2 and the reference line L2 (the principal ray of the beam 1 is scanned). The angle formed by the line (when perpendicular to the scanning line on the surface 20) is set to 64.3 degrees. Therefore, the opening angle γ of the beams 1 and 2 is 4.3 degrees. Both beams 1 and 2 are made “parallel beams” by the coupling lenses 3 and 4. The deflector is a “rotating polygon mirror” having six deflecting reflecting surfaces, and the distance from the rotating shaft 7A to the deflecting reflecting surface 7 is 18 mm.
When the beam 1 is reflected by the deflecting reflecting surface 7 and its principal ray coincides with the reference line L1, the "incident angle of the beam 1 to the deflecting reflecting surface 7" is 30 degrees, and the beam 2 is reflected by the deflecting reflecting surface 7. When the principal ray coincides with the reference line L2, the "incident angle of the beam 2 on the deflecting / reflecting surface 7" is 32.15 degrees. Of course, the reference lines L1 and L2 are the deflection rotation surfaces (see FIG. Projections to the plane shown in Fig. 1 are parallel to each other.
[0010]
The cylinder lenses 5 and 6 of the second optical system are the same and have the following data.
First surface (incident side) radius of curvature in the sub-scanning direction: R (cylinder surface): 48 mm
2nd surface: Plane center wall thickness: 3mm
Refractive index at working wavelength = 1.511118.
[0011]
The scanning lens 11 of the third optical system is “coaxial aspheric surface” on both sides, the coordinate in the optical axis direction is X, the distance from the apex is r, the paraxial radius of curvature is RN, the conic constant is KN, and the higher order The coefficients are RNA4, RNA6, RNA8, RNA10,... (N is N = 1 on the incident side, N = 2 on the exit side),
X = r ² / [RN + RN · √ {1- (1 + KN) r ² / RN ² }] + RNA4 · r ⁴ + RNA6 · r ⁶ + RNA8 · r ⁸ + RNA10 · r ¹⁰
Can be expressed as Assuming that the refractive index at the used wavelength of the material of the scanning lens 11 is N and the center thickness is D, the data of the aspherical shape and the refractive index / center thickness are as follows.
R1 -264.0
K1 2.449
R1A4 2.594E-07
R1A6 1.256E-11
R1A8 -2.416E-13
R1A10 4.910E-17
D 23.3
N 1.52441
R2-61.3
K2 -0.0213
R2A4 5.949E-07
R2A6 1.120E-12
R2A8 2.452E-14
R2A10-3.969E-17
In notation above, for example, "E-17" refers to 10 ^17, this number is the according to the immediately preceding value. The same applies hereinafter.
[0012]
The scanning lens 12 of the third optical system is “non-arc-shaped” in both main scanning directions. The non-arc shape is such that the coordinate in the optical axis direction is X, the coordinate in the main scanning direction is Y, the paraxial radius of curvature is Rmn, the conic constant is Kmn, the higher order coefficients are an, bn, cn, dn,. , Where n = 1 for the incident side and n = 2 for the exit side.
X = Y ² / [Rmn + Rmn · √ {1− (1 + Kmn) Y ² / Rmn ² }] + an · Y ⁴ + bn · Y ⁶ + cn · Y ⁸ + dn · Y ¹⁰
Assuming that the refractive index at the used wavelength of the material of the scanning lens 12 is N and the center thickness is D, the data of the aspherical shape and the refractive index / center thickness are as follows.
Rm1 -340.0
Km1-62.03
a1 -1.047E-08
b1-9.302E-12
c1-1.271E-15
d1 1.863E-19
D 3.5
N 1.52441
Rm2 -680.0
Km2 19.12
a2-1.314E-07
b2-2.256E-12
c2 1.004E-16
d2-2.522E-20.
[0013]
The scanning lens 12 has a sub-scanning radius of curvature (a radius of curvature in a cross section parallel to the sub-scanning direction): rns (Y) (where n is the incident side and n = 1, and the exit side is n = 2). Depending on the coordinate of the direction: Y,
rns (Y) = RnS + en · Y ² + fn · Y ⁴ + gn · Y ⁶ + hn · Y ⁸ + in · Y ¹⁰ + jn · Y ¹²
(RnS is a radius of curvature at Y = 0), and is specified by the following data.
[0014]
R1S = -32.01
e1 = 1.385E-03, f1 = −4.354E-07, g1 = 2.324E-11, h1 = 3.250E-15, i1 = −2.023E-19, j1 = −6.203E-23
R2S = -16.97
e2 = f2 = g2 = ... = 0.
[0015]
Distance between the reflection point of the reference line L1 on the deflecting reflection surface and the first surface of the scanning lens 11: 44.4 mm, distance between the second surface of the scanning lens 11 and the first surface of the scanning lens 12: 50.4 mm, scanning The distance between the second surface of the lens 12 and the surface to be scanned is 107.1 mm.
Further, the distance from the cylinder lens of the beam 1 to the deflecting reflecting surface when the principal ray of the reflected beam by the deflector coincides with the reference lines (L1, L2): 91.92 mm, from the cylinder lens of the beam 2 to the deflecting reflecting surface Distance: 91.66 mm.
When the beam 1 coincides with the reference line L1, the distance between the two beams on the deflection reflection surface is 0.62 mm. When two beams are projected onto the deflection rotation surface, the beams 1 and 2 intersect after the deflection reflection surface. . This can increase the overlapping portion of the range that can be two-beam scanning on the surface to be scanned, the deflecting reflective surface to allow scanning of a wide range even smaller (claim 4).
[0016]
As shown in FIG. 1, the distance from the reference line L1 to the first surface vertex of the scanning lens 11 is Δ1, the distance from the reference line L2 to the first surface vertex of the scanning lens 11 is Δ2, and the reference line L1 to the scanning lens 12 Δ1 ′ and the distance from the reference line L2 to the first surface vertex of the scanning lens 12 is Δ2 ′ (all on the incident beam side to the deflector, that is, upward in FIG. 1 in the plus direction) Assuming that Δ1 = 1.00 mm, Δ2 = 0.45 mm, Δ1 ′ = 0.90 mm, Δ2 ′ = 0.35 mm, the “shift condition” in claim 1 is satisfied. Tilt amounts: α and β are both 0, and the optical axes of the scanning lenses 11 and 12 are parallel to each other.
[0017]
As shown in FIG. 2, when the deflection reflecting surface 7 and its rotation axis 7A do not coincide with each other, the reflection point of the beam toward the periphery is the incident beam side (in the figure) with respect to the reflection point C of the beam toward the center. Shifts upward). Therefore, optical characteristics deteriorate unless at least one of the scanning lenses of the third optical system is shifted to the incident beam side with respect to all the reference lines. FIG. 3 shows the curvature of field in the main and sub-scanning directions and the constant velocity (deviation amount from ideal image height × 100 / ideal image direction (%)) for the two beams in the first embodiment. All of these are well corrected.
In Example 1, S1 (+) = 0.01, S1 (−) = 0.11, S2 (+) = 0.57, S2 (−) = − 0.37,
(S1 (+)-S1 (-)) x (S2 (+)-S2 (-)) = -0.094 <0
Thus, conditional expression (1) is satisfied ( claim 1 ).
And M1 (+) = 0.16, M1 (-) = 0.06, M2 (+) =-0.14, M2 (-) = 0.11,
(M1 (+)-M1 (-)) x (M2 (+)-M2 (-)) = -0.025 <0
Thus, the conditional expression (2) is satisfied ( claim 2 ).
That is, in Example 1, the conditional expression (1), (2) both are satisfied, both main and sub-scanning direction good imaging performance can be obtained (Claim 3).
Since the beams 1 and 2 are incident on the deflector with an “open angle”, the sag amount is different between the beam 1 and the beam 2, and the imaging performance is different. Therefore, if conditional expressions (1) and (2) are not satisfied, good imaging performance can be given to one beam, but good imaging performance can be given to the other beam. I can not let you. By satisfying conditional expressions (1) and (2), a balanced design can be achieved.
[0018]
Comparative Example 1
As a comparative example for Example 1, the following changes are made to Example 1.
[0019]
Δ1 = 0.00 mm, Δ2 = −0.55 mm, Δ1 ′ = 0.00 mm, Δ2 ′ = − 0.55 mm
At this time, since the scanning lens 11 is not shifted with respect to the reference line L1, “the optical axis of at least one scanning optical element of the third optical system is on the deflecting reflection surface when viewed from all the reference lines”. It does not satisfy the condition of “deployed by shifting to the beam side”. The field curvature and constant velocity with respect to the beams 1 and 2 at this time are as shown in FIG.
Further, S1 (+) = 0.92, S1 (−) = − 0.73, S2 (+) = 1.37, S2 (−) = − 1.21,
(S1 (+) − S1 (−)) × (S2 (+) − S2 (−)) = 4.257> 0,
M1 (+) = − 0.26, M1 (−) = 0.21, M2 (+) = − 0.79, M2 (−) = 0.19,
(M1 (+) − M1 (−)) × (M2 (+) − M2 (−)) = 0.461> 0
Therefore, neither of the conditional expressions (1) and (2) is satisfied.
[0020]
Example 2
The following changes were made to Example 1.
[0021]
Δ1 = 0.80 mm, Δ2 = 0.25 mm, Δ1 ′ = 0.80 mm, Δ2 ′ = 0.25 mm. That is, the shift condition in claim 1 is satisfied.
When the tilt amount of the scanning lens 11 with respect to the reference lines L1 and L2 is α, and the tilt amount of the scanning lens 12 with respect to the reference lines L1 and L2 is α ′ (counterclockwise is positive),
α = −0.07 degrees, α ′ = 0.40 degrees That is, the scanning lenses 11 and 12 are also tilted with respect to the reference lines L1 and L2. By providing tilt with shifting, the degree of freedom in design increases, the conditions of the conditional expressions (1) and (2) can be satisfied, and good optical characteristics can be obtained.
[0022]
FIG. 5 shows the field curvature and constant velocity of main scanning and sub-scanning of the two beams according to the second embodiment. Both are corrected well.
S1 (+) = − 0.06, S1 (−) = 0.26, S2 (+) = 0.40, S2 (−) = − 0.22,
(S1 (+) − S1 (−)) × (S2 (+) − S2 (−)) = − 0.20 <0
M1 (+) = 0.12, M1 (−) = 0.09, M2 (+) = − 0.20, M2 (−) = 0.14,
(M1 (+) − M1 (−)) × (M2 (+) − M2 (−))) = − 0.01 <0
Therefore, both conditional expressions (1) and (2) are satisfied.
[0023]
Example 3
The following changes were made to Example 1.
The distance from the cylinder lens 3 of the beam 1 to the deflecting reflecting surface 7 when the principal ray of the reflected beam by the deflecting reflecting surface 7 coincides with the reference lines L1 and L2, 91.92 mm, from the cylinder lens 4 of the beam 2 to the deflecting reflecting surface Distance to 7: 91.88 mm.
When the beam 1 coincides with the reference line L1, the distance between the two beams on the deflection reflection surface 7 is 0.0 mm, and when the two beams are projected onto the deflection rotation surface, they intersect on the deflection reflection surface.
Δ1 = 0.80 mm, Δ2 = 0.75 mm, Δ1 ′ = 0.80 mm, Δ2 ′ = 0.75 mm, and “the optical axis of at least one scanning optical element of the third optical system is all the above-mentioned “It is arranged to be shifted to the beam side toward the deflecting reflecting surface as viewed from the reference line”.
[0024]
Tilt amounts: α = −0.061 degrees and α ′ = 0.35 degrees.
FIG. 6 shows the field curvature and constant velocity in the main and sub-scanning directions for the two beams 1 and 2 of the third embodiment. These are all corrected well. Also,
S1 (+) = − 0.02, S1 (−) = 0.22, S2 (+) = 0.56, S2 (−) = − 0.12.
(S1 (+) − S1 (−)) × (S2 (+) − S2 (−)) = − 0.16 <0
M1 (+) = 0.11, M1 (−) = 0.10, M2 (+) = 0.03, M2 (−) = 0.04,
(M1 (+) − M1 (−)) × (M2 (+) − M2 (−)) = − 0.001 <0
Therefore, both conditional expressions (1) and (2) are satisfied.
In the above embodiment, two light sources LD1 and LD2 are used, and an embodiment of simultaneous scanning with two beams has been described. Needless to say, three or more light sources can be used. When three or more light sources are used, the principal rays of the two or more beams can overlap each other in a state in which the beam from each light source is projected onto the deflection rotation surface.
[0025]
【The invention's effect】
As described above, according to the present invention, a novel multi-beam scanning device can be realized.
[0026]
The multi-beam scanning device according to the present invention does not require an expensive beam combining means such as a polarizing beam splitter, and can be realized at a low cost with a small number of parts. The characteristics can be improved.
[0027]
According to the first to third aspects of the present invention, by satisfying the conditions (1) and / or (2), the sub-scanning direction and / or the main scanning direction can be performed for a plurality of beams at a low cost and with a small number of parts. Excellent field curvature characteristics (small diameter and stable sub-scanning beam spot diameter) can be obtained.
According to the fourth aspect of the present invention, when a plurality of beams are projected from the light source side into the deflection rotation surface, at least two beams intersect after the deflection surface, so that two beams are formed on the surface to be scanned. The overlapping portion of the scanning range can be increased, and a wide range of scanning can be performed even if the deflection reflection surface is small.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining one embodiment of a multi-beam scanning apparatus according to the present invention.
FIG. 2 is a diagram for explaining the significance of the shift of the scanning imaging element of the third optical system.
FIG. 3 is a diagram showing field curvature and constant velocity with respect to beams 1 and 2 according to the first embodiment.
4 is a graph showing curvature of field and constant velocity with respect to beams 1 and 2 of Comparative Example 1. FIG.
FIG. 5 is a diagram showing field curvature and constant velocity with respect to beams 1 and 2 according to the second embodiment.
6 is a diagram showing field curvature and constant velocity with respect to beams 1 and 2 of Example 3. FIG.
[Explanation of symbols]
1, 2 LD (semiconductor laser) as light source
3, 4 Coupling lenses 5 and 6 as the first optical system Cylinder lens 7 as the second optical system 7 Deflection / reflecting surface 7A Rotating shafts 11 and 12 of the deflector Scanning lens L1 forming the scanning imaging element of the third optical system , L2 Reference lines Δ1, Δ2, Δ1 ′, Δ2 ′ Shift amount

Claims (4)

Multiple light sources;
A plurality of first optical systems that respectively couple the plurality of light sources;
A second optical system for condensing the beam from the first optical system in a substantially linear shape long in the main scanning direction;
Deflection having a deflecting reflecting surface in the vicinity of the substantially linear condensing part, deflecting a plurality of beams from the second optical system at an equiangular velocity, and the deflecting reflecting surface and the rotation axis thereof being separated by a certain distance And
A third optical system including a scanning imaging element that condenses the deflected deflected beams toward the surface to be scanned and scans the surface to be scanned at a substantially constant speed;
The plurality of beams from the second optical system are directed from the same side in the main scanning direction outside the scanning imaging element toward the deflecting reflection surface,
At least two of the plurality of beams from the second optical system have an opening angle in the deflection rotation plane,
An imaging position in the sub-scanning direction at both the most peripheral image heights of one of the beams from the plurality of light sources. S1 (+) , S1 (-) , The sub-scanning direction imaging position at the most peripheral image height of the beam by one light source other than the above S2 (+) , S2 (-) And when these are the conditions:
(1) (S1 (+)-S1 (-)) × (S2 (+)-S2 (-)) < 0
A multi-beam scanning device characterized by satisfying Multiple light sources;
A plurality of first optical systems that respectively couple the plurality of light sources;
A second optical system for condensing the beam from the first optical system in a substantially linear shape long in the main scanning direction;
Deflection having a deflecting reflecting surface in the vicinity of the substantially linear condensing part, deflecting a plurality of beams from the second optical system at an equiangular velocity, and the deflecting reflecting surface and the rotation axis thereof being separated by a certain distance And
A third optical system including a scanning imaging element that condenses the deflected deflected beams toward the surface to be scanned and scans the surface to be scanned at a substantially constant speed;
The plurality of beams from the second optical system are directed from the same side in the main scanning direction outside the scanning imaging element toward the deflecting reflection surface,
At least two of the plurality of beams from the second optical system have an opening angle in the deflection rotation plane,
The imaging position in the main scanning direction at the most peripheral image height of one of the beams from the plurality of light sources. M1 (+) , M1 (-) , The imaging position in the main scanning direction at the most peripheral image height of the beam by one light source other than the above M2 (+) , M2 (-) And when these are the conditions:
(2) (M1 (+)-M1 (-)) × (M2 (+)-M2 (-)) < 0
A multi-beam scanning device characterized by satisfying Multiple light sources;
A plurality of first optical systems that respectively couple the plurality of light sources;
A second optical system for condensing the beam from the first optical system in a substantially linear shape long in the main scanning direction;
A deflector having a deflecting / reflecting surface in the vicinity of the substantially linear condensing unit, deflecting a plurality of beams from the second optical system at an equiangular velocity, and having a constant distance between the deflecting / reflecting surface and a rotation axis When,
A third optical system including a scanning imaging element that condenses the deflected deflected beams toward the surface to be scanned and scans the surface to be scanned at a substantially constant speed;
The plurality of beams from the second optical system are directed from the same side in the main scanning direction outside the scanning imaging element toward the deflecting reflection surface,
At least two of the plurality of beams from the second optical system have an opening angle in the deflection rotation plane,
The imaging position in the main scanning direction at the most peripheral image height of one of the beams from the plurality of light sources. M1 (+) , M1 (-) , Sub-scanning direction imaging position S1 (+) , S1 (-) , The imaging position in the main scanning direction at the most peripheral image height of the beam by one light source other than the above M2 (+) , M2 (-) , Sub-scanning direction imaging position S2 (+), S2 (-) And when these are the conditions:
(1) (S1 (+)-S1 (-)) × (S2 (+)-S2 (-)) < 0
(2) (M1 (+)-M1 (-)) × (M2 (+)-M2 (-)) < 0
A multi-beam scanning device characterized by satisfying both. The multi-beam scanning device according to any one of claims 1 to 3,
A multi-beam scanning apparatus characterized in that at least two beams intersect after the deflection surface when projected onto the deflection rotation surface.

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