JPH1138341A - Multibeam scanning device and scanning image forming optical system therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively correct and reduce the bend of a scanning line, by determining the tilt in the sub-scanning cross section on a beam incident position of a correction refractive surface in accordance with the incident position so as to correct the bent of a scanning line of the beam. SOLUTION: The peripheral part of light beam is cut off by passing through the opening part of an aperture 20 and the beam is formed to have a proper cross sectional shape. The formed beam is converged in the corresponding direction of scanning by means of a cylindrical lens 25. A reflected beam by a deflection/reflection surface is deflected at a constant angular velocity accompanying the constant speed revolution of a polygon mirror 30, transmitted through lenses 41-43, converged on a surface 50 to be scanned by lens action as a light spot and optically scans the surface 50 to be scanned. In this case, any lens surface of the lenses 41-43 of the scanning image forming optical system is made to be a correction refractive surface, the tilt of the correction refractive surface in the sub-scanning cross section at the incident position of at least one beam from among plural incident beams is adjusted and the bend of scanning line of the beam is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam scanning device and a scanning imaging optical system of the multi-beam scanning device.

[0002]

2. Description of the Related Art In an optical scanning apparatus known in connection with an image forming apparatus such as a digital copying machine or an optical printer, a plurality of beams (light beams in this specification) scan a surface to be scanned with a plurality of lines. A “multi-beam scanning device” that performs optical scanning at the same time has been proposed and is intended for practical use.
One of the important problems in the multi-beam scanning device is a problem of “scanning line bending”. Generally, in an optical scanning device, a beam from a light source side is deflected by an optical deflector, and is condensed as a light spot on a surface to be scanned by a scanning image forming optical system to optically scan the surface to be scanned. If the beam to be deflected is a single beam, it is deflected in a plane including the optical axis of the scanning image forming optical system, so that scanning line bending does not occur in principle.
However, in the case of a multi-beam scanning device, a part of the plurality of beams is inevitably deflected at a portion off the optical axis of the scanning imaging optical system, and such a beam causes a scanning line bending. Let me do it.

As described above, the scanning line bending caused by the beam being deflected at the "off-axis portion of the scanning image forming optical system" is a characteristic inherent to the optical arrangement of the multi-beam scanning apparatus. In this specification, this is referred to as "scanning line bending inherent to the multi-beam scanning device".

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to effectively correct and reduce scanning line bending inherent in a multi-beam scanning device.

[0005]

The scanning image forming optical system according to the present invention is composed of a light deflector that divides a plurality of beams from a light source having a plurality of light emitting portions deviated to one side of the optical axis at least in a direction corresponding to the sub-scanning direction. The scanning imaging optical system of a multi-beam scanning device that deflects and condenses as a plurality of light spots separated in the sub-scanning corresponding direction on the surface to be scanned by the scanning imaging optical system and optically scans a plurality of lines simultaneously. Therefore, it has the following features (claim 1). That is, the scanning image forming optical system has a “correcting refraction surface that corrects a scanning line curve inherent to the multi-beam scanning device”. The correction refraction surface is such that the inclination of the beam in the sub-scan section at the incident position of at least one beam among the plurality of beams incident on the correction refraction surface is the scanning line bending (scanning line bending unique to the multi-beam scanning device). )
Is determined in accordance with the incident position so as to correct the above. " The “sub-scanning corresponding direction” is a direction corresponding to the sub-scanning direction on the optical path from the light source to the surface to be scanned, and a direction corresponding to the main scanning direction on the optical path is referred to as a “main scanning corresponding direction”. As the “optical deflector”, a rotating polygon mirror, a rotating single mirror or a rotating two-face mirror can be used.

"The scanning image forming optical system focuses a plurality of beams from the light source side as a plurality of light spots on the surface to be scanned."
This includes a case where the function of the scanning imaging optical system acts on a plurality of incident beams and a plurality of deflection beams immediately before the optical deflector, and a case where the function acts only on the plurality of deflection beams. Japanese Patent Application Laid-Open No. 6-75162 discloses a "rotating lens mirror" which is integrated with a deflecting / reflecting surface and has a refracting surface having an incident surface to the deflecting / reflecting surface and an exit surface from which the reflected beam exits. . The function of this rotating lens mirror is to "act on the immediately preceding incident beam and the deflected beam to the optical deflector". The “scanning optical system” in the present invention may include such a rotating lens mirror. In such a case, the “incident surface and / or exit surface” is referred to as a “correction refractive surface”. You can also.

The correction refraction surface may be formed as one surface of a lens included in the scanning image forming optical system, or may be formed as two or more surfaces, and a desired effect is obtained by combining the correction effects of the two or more surfaces. May be realized.

The “sub-scan section” means “a plane section orthogonal to the main scanning direction at a position close to the refraction surface” with respect to the refraction surface located closer to the surface to be scanned than the optical deflector.
When the scanning image forming optical system includes a rotating lens mirror, the plane of incidence of the rotating lens mirror is defined as a “plane section parallel to the principal ray of the incident beam from the light source side and the direction corresponding to the sub-scanning” as the sub-scanning section. Regarding the exit side surface, a “plane section parallel to the principal ray in the exit light beam and the direction corresponding to the sub-scanning” is defined as the sub-scanning section.

As described above, "scanning line bending inherent in a multi-beam scanning apparatus" is a scanning line bending caused by beam deflection being performed at a portion off the optical axis of the scanning image forming optical system. In other words, the term "scanning line bending" occurs when a multi-beam scanning apparatus is designed without providing the "scanning line bending correction function by the correction refraction surface" in the scanning image forming optical system. That is, the scanning line curvature inherent to the multi-beam scanning device is determined by the design of the multi-beam scanning device, and therefore, a correction refraction surface that corrects such scanning line bending can be determined in design. It is.

The scanning image forming optical system can have various configurations including a correction refracting surface. The two components are "a lens provided between an optical deflector and a surface to be scanned, and these two lenses. And has a function of converging the deflected beam as a light spot on the surface to be scanned. " ). Of course, between the optical deflector and the surface to be scanned, in addition to such a scanning image forming optical system, a “plane mirror for bending the optical path” may be appropriately provided according to the optical system layout of the multi-beam scanning device. (Claim 2).

In the scanning image forming optical system of the multi-beam scanning apparatus according to the second aspect, "one surface of the long lens is a correction refraction surface, and the center of curvature of the correction refraction surface in the sub-scan section is the main scanning direction. (The center line of curvature connected to the curve becomes a three-dimensional curve.)
A "dimensional curve" is a curve that is not in the same plane).

The scanning image forming optical system according to any one of the first to third aspects of the present invention is characterized in that a function of making the optical scanning by a plurality of beams deflected at an equal angular velocity by the optical deflector uniform (scanning image forming optical system). Is an fθ lens, it can have an “fθ function” (claim 4). Further, the scanning imaging optical system according to any one of claims 1 to 4 is capable of “deflection by an optical deflector. (A function to make the vicinity of the starting point and the position of the surface to be scanned a geometric conjugate relationship in the sub-scanning corresponding direction).

According to a sixth aspect of the present invention, there is provided a multi-beam scanning apparatus comprising: a light beam deflector deflects a plurality of beams from a light source having a plurality of light-emitting portions deflected to one side of an optical axis in at least a sub-scanning direction; A multi-beam scanning device that converges as a plurality of light spots separated in a sub-scanning corresponding direction on a surface to be scanned by an image optical system and optically scans a plurality of lines at the same time. A scanning image forming optical system according to any one of Items 1 to 5, is used.

According to a seventh aspect of the present invention, there is provided a multi-beam scanning apparatus, wherein at least in a direction corresponding to the sub-scanning direction, a plurality of beams from a light source having a plurality of light emitting portions deflected to one side of the optical axis are deflected at an equal angular velocity by an optical deflector. A multi-beam scanning device that converges as a plurality of light spots separated in a sub-scanning corresponding direction on the surface to be scanned by a scanning image forming optical system and optically scans a plurality of lines at the same time. A scanning image forming optical system according to claim 4 is used.

The multi-beam scanning device according to claim 8, wherein "a plurality of beams from a light source side having a plurality of light emitting portions deviated to one side of the optical axis at least in the sub-scanning corresponding direction,
A plurality of linear images are formed in the vicinity of the deflecting / reflecting surface of the optical deflector in the main scanning direction, and are deflected at the same angular velocity by the optical deflector. Focused as multiple light spots separated in the direction,
Multi-beam scanning device that scans multiple lines simultaneously. "
A scanning image forming optical system according to claim 5, wherein the scanning image forming optical system has a function of equalizing light scanning by a plurality of beams deflected by an optical deflector at an equal angular velocity. It is characterized by the following.

In the multi-beam scanning device according to the sixth, seventh or eighth aspect, "the number of light-emitting portions in the light source is two" (claim 9).

[0017]

FIG. 1 is a diagram for explaining an embodiment of a multi-beam scanning apparatus according to the present invention. (A) shows a state where the optical arrangement of the multi-beam scanning device is viewed from the direction corresponding to the sub-scanning. 1A, a beam emitted from a light source 10 is coupled to a coupling lens 15.
Is coupled to the subsequent optical system. The coupling action of the coupling lens 15 may be such that the beam transmitted through the coupling lens 15 becomes a “parallel light beam” or “a weakly divergent or weakly converging light beam”. it can.

The coupled beam passes through the aperture of the aperture 20 to block the periphery of the light beam, and is "beam-shaped" into an appropriate beam cross-sectional shape.
The beam-shaped beam is condensed by the cylindrical lens 25 in the direction corresponding to the sub-scanning (the direction orthogonal to the drawing in FIG. 1A), and the optical path is bent by the optical path bending mirror 27 to form an “optical deflector”. An image is formed as a long line image in the main scanning corresponding direction near the position of the deflection reflection surface of the polygon mirror 30. The beam reflected by the deflecting / reflecting surface is deflected at a constant angular velocity with the rotation of the polygon mirror 30 at a constant speed, passes through the lenses 41, 42, and 43, and the surface to be scanned (substantially, photoconductive The light is condensed as a light spot on the photosensitive surface (photosensitive surface of the photosensitive member) 50, and the scanned surface 50 is optically scanned. In the embodiment of FIG.
42 and 43 constitute a “scanning optical system”. Lens 4
3 is a "long toroidal lens".

FIG. 1B shows the relationship between the light source 10 and the coupling lens 15 in FIG. Light source 1
Reference numeral 0 denotes a semiconductor laser array having a monolithic structure, which has two light-emitting portions, and these two light-emitting portions 101 and 1 are provided.
Numeral 02 is disposed so as to be deviated to one side of the optical axis with respect to the “optical axis” of the coupling lens 15 in the sub-scanning corresponding direction (the vertical direction in FIG. 1B).
For convenience of illustration, the arrangement of the light emitting units 101 and 102 is shown in an enlarged state in the sub-scanning corresponding direction. Since two beams are emitted from the light source 10 in this manner, two light spots are condensed and formed on the surface 50 to be scanned. However, since the light emitting units 101 and 102 are shifted from each other in the sub-scanning corresponding direction, And light spots are also formed separately in the sub-scanning direction.

In the optical path from the coupling lens 15 to the lens 43, the coupling lens 15, the cylindrical lens 25, and the lens 41 are "optical axis aligned" with each other.
However, the lenses 42 and 43 are "shifted" in the sub-scanning corresponding direction as described later. As shown in FIG. 1B, the light emitting units 101 and 102 of the light source 10 are deviated from the optical axis of the coupling lens 15 in the sub-scanning corresponding direction, so that the light is emitted from the light emitting units 101 and 102. When each beam is deflected by the polygon mirror 30, “the cross section including the optical axis and parallel to the main scanning direction” of the scanning imaging optical system constituted by the lenses 41, 42, and 43.
Since the transmitted light passes through a portion separated from the scanning beam, it is assumed that “the scanning imaging optical system does not include the correction refraction surface”. "Abbreviated as" inherent scan line bending "). Therefore, the scanning image forming optical system is changed to the lens 4.
Either of the lens surfaces 1, 42 and 43 is used as a correction refracting surface,
The “inclination in the sub-scan section” of the correction refraction surface at the incident position of at least one of the plurality of beams incident on the correction refraction surface is adjusted to correct the scan line bending of the beam. Item 1). In the embodiment shown in FIG. 1, the incident side surface of the lens 43, which is a long toroidal lens, is a "correcting refractive surface" (claim 3). "If the shape of the correction refraction surface is a non-circular shape" in the sub-scan section, it is also possible to correct the scanning line bending for each of the two beams.

The "scanning image forming optical system" composed of the lenses 41, 42 and 43 includes two lenses 41 and 42 provided between the optical deflector 30 and the surface 50 to be scanned. And one long lens 43 provided closer to the scanned surface 50 than the above lens, and has a function of condensing the deflected beam as a light spot on the scanned surface (claim 2). The scanning image forming optical system has a function of equalizing the speed of optical scanning by a plurality of beams deflected by the optical deflector 30 at a constant angular velocity (claim 4). There is a function of making the vicinity of the position of the reflection point when the principal ray of the beam coincides with the optical axis of the lens 41 in the sub-scanning corresponding direction) and the position of the surface to be scanned 50 a geometric optical conjugate relationship in the sub-scanning corresponding direction. (Claim 5).

The multi-beam scanning apparatus shown in FIG. 1 uses the optical deflector 30 to “divide a plurality of beams from the light source 10 having a plurality of light emitting portions 101 and 102 deviated to one side of the optical axis at least in the sub-scanning corresponding direction. The light is deflected and condensed as a plurality of light spots separated in the sub-scanning corresponding direction on the surface to be scanned 50 by the scanning image forming optical systems 41, 42, and 43.
A multi-beam scanning apparatus for simultaneously scanning a plurality of lines with light, having the “scanning image forming optical system” according to any one of claims 1 to 5 (claim 6), wherein the optical deflector 30 is Each beam to be deflected at an angular velocity is scanned by the scanning and imaging optical system 4.
A multi-beam scanning device that converges a plurality of light spots separated in a sub-scanning corresponding direction on a surface to be scanned 50 by a light source 1, 42, and 43, and simultaneously and uniformly scans a plurality of lines with light. ), A plurality of beams from the light source side are formed as a plurality of linear images long in the main scanning corresponding direction in the vicinity of the deflecting reflection surface of the optical deflector 30 and are deflected at an equal angular velocity by the optical deflector 30 to form a scanning image. This is a multi-beam scanning device that converges a plurality of light spots on the scanned surface 50 in the sub-scanning corresponding direction by the optical systems 41, 42, and 43, and simultaneously and uniformly scans a plurality of lines with light ( Claim 8),
The light source 10 has two light emitting units 101 and 102 (claim 9).

[0023]

EXAMPLE The embodiment shown in FIG. 1 was constructed as a specific example as follows. As the light source 10, an interval between the light emitting units 101 and 102: 2.5 μm, an emission wavelength: 780
nm using a “monolithic semiconductor laser array”
The arrangement direction of the light emitting units 101 and 102 is set as the direction corresponding to the sub-scanning direction, and the light emitting unit 101 (the light emitting unit on the side closer to the optical axis of the coupling lens 15) is positioned at −2.5 μm (−0) from the optical axis of the coupling lens 15. .0025 mm) in the sub-scanning corresponding direction (a negative sign means a downward displacement of the optical axis in FIG. 1B). Therefore, the light emitting unit 10
No. 2 deviates from the optical axis in the sub-scanning corresponding direction by −5.0 μm. Polygon mirror 3 as an optical deflector
0 is the number of deflecting / reflecting surfaces: 6, the radius of the inscribed circle of the deflecting / reflecting surface: 1
The angle between the incident direction of the beam incident on the polygon mirror 27 from the side of the optical path bending mirror 27 and the optical axis of the lens 41 of the scanning image forming optical system is 60 degrees.

The optical system on the optical path from the light source 10 to the polygon mirror 30 is referred to as a "first group", and the optical system on the optical path from the polygon mirror 30 to the surface 50 to be scanned is referred to as a "second group".
The cover glass of the “semiconductor laser array unit” that is the light source 10, the deflecting and reflecting surface, and the radius of curvature of the lens surface of each lens
(Paraxial radius of curvature for those not having an arc shape) is Rm for the main scanning corresponding direction and Rs for the sub-scanning corresponding method direction.
Where D is the distance on the optical axis and N is the refractive index of the material.
An amount having a "length dimension" is in "mm" units.

First group data: Surface number Rm Rs DN 0 4.29 Light-emitting part 1 ∞ ∞ 0.30 1.511 Cover glass 2 ∞ 2.00 3 ∞ ∞ 2.50 1.675 Coupling lens 4 -5.3856 -5.3856 26.55 5 ∞ 61.86 3.00 1.511 Cylindrical lens 6 ∞ ∞ 123.66.

The exit side surface (surface number: 4) of the coupling lens is a "coaxial aspheric surface", and the coupled light beam is a "substantial parallel light beam". That is, the above-mentioned coaxial aspherical surface is a well-known aspherical surface expression in which the optical axis direction is the X axis and the optical axis orthogonal direction is the Y axis. When the sixth, eighth, and tenth aspheric coefficients are A, B, C, and D, they have the following values. R = -5.3856, K = -0.0074, A = 4.7E-4, B = 1.27E-5, C = 2.94E-7, D = 9.35E-9. “E-4” and the like indicate “power”. For example, the above “E-4” means “10 to ⁴ ”, and this value is multiplied by the numerical value immediately before it.

In the second group, Z represents the shift amount of the optical axis in the direction corresponding to the sub-scanning (the upward shift of the optical axis in FIG. 1B is defined as “positive”). Second group data: Surface number Rm Rs DNZ 0 ∞ 32.81-Polygon mirror 1 -137.015 -137.015 18.00 1.5721-Lens 41 2 -112.155 -112.155 17.00 3 ∞ ∞ 23.50 1.5721 +0.6 Lens 42 4 -148.565 -148.565 110.50 5 -700 -44.3 3.00 1.5721 +0.6 Lens 43 6 -700 -20.32 86.77 Both sides of the lens 41 are "coaxial spherical", and the exit side of the lens 42 (the above surface number: 4) is also "coaxial spherical". . Lens 4
The optical axis of the lens 2 and the lens 43 are shifted by “+0.6 mm” in the sub-scanning corresponding direction with respect to the optical axis position of the lens 41. + Means an upward shift in FIG. 1 (b).

The curvature Cs (5) in the sub-scan section of the surface of surface number 5 in the second group, that is, the surface on the optical deflector side of the lens 43 which is a "long toroidal lens" corresponds to the main scanning. Cs (5) = (1 / Rs (5)) + {b _j Y ** j (j = 1, 2, 3,...) Where Y is the coordinate of the direction (the origin is the optical axis position of the lens 41). In the equation represented by the following expression, Rs (5) (the paraxial radius of curvature in the sub-scan section including the optical axis) and a coefficient: b _j are given. “Y ** j” represents Y raised to the j-th power. Rs (5) = - 44.3, b 2 = -3.65E-7, b 4 = -5.33E-12, b 6 = -4.59E-16, b 8 = 6.69E-20, b ₁₀ = −5.42E-24, b ₁₂ = 1.47E−28 Coefficient of the odd-order term of Y: b _j (j = 1, 3, 5,
7,. . ) Are all 0, and therefore, the change of the curvature in the sub-scanning cross section in the main scanning corresponding direction is symmetric with respect to the coordinate: Y at the origin. The exit side surface of the lens 43 is a normal toroidal surface.

The optical arrangement specified by the above data is called a "design standard". This design criterion is “an optical system in which the correction refraction surface does not have a scanning line bending correction function”, and the scanning line bending generated at this time is “scanning line bending unique to the multi-beam scanning device”. The “inherent scan line bend” for the beam from 101 is shown in FIG.
In FIG. 2B, “unique scanning line bending” for the beam from the light emitting unit 102 is indicated by reference numeral 2-1 ′.
2-2 '.

In this embodiment, the surface of the lens 43 on the optical deflector side (the fifth surface of the second group) is a correction refracting surface,
At each incident position of the beam from the light emitting unit 101, the inclination in the sub-scanning cross section was set as follows according to the coordinate Y in the main scanning corresponding direction.

[0031]

Of course, the change in the tilt angle in the entire main scanning direction can be obtained by smoothly connecting the changes, and if necessary, it can be analytically expressed by a polynomial or the like. Due to such an inclination in the sub-scan section, the “curvature center line” connecting the centers of curvature in the sub-scan section on the correction refraction surface becomes a three-dimensional curve (claim 3).

The “scanning line bend after correction by the correction refraction surface” indicates that the beam from the light emitting unit 101 is the same as that in FIG.
FIG. 2A shows “as shown by reference numeral 2-1”, and the beam from the light emitting unit 102 becomes “as shown by reference numeral 2-2” in FIG. 2B. With respect to the beam from the light emitting unit 101, the scan line bending is substantially completely corrected,
The beam from the light emitting unit 102 is corrected and reduced very effectively because the scanning line bending amount is 0.005 mm at the maximum. Therefore, it is possible to realize multi-beam scanning using two light spots whose scanning line curvature is corrected extremely well. Note that the constant velocity characteristics (fθ characteristics) in the embodiment are good as shown in FIG.

[0034]

As described above, according to the present invention, a novel multi-beam scanning device and a scanning image forming optical system for the multi-beam scanning device can be realized. Since the scanning image forming optical system of the present invention has a correcting refraction surface for correcting the scanning line bending inherent to the multi-beam scanning device, the scanning line bending which inevitably occurs in the design of the multi-beam scanning device can be effectively corrected and reduced. (Claims 1 to 5). Further, the scanning image forming optical system according to the fourth aspect has a function of equalizing the optical scanning by a plurality of beams deflected at a constant angular velocity. Correction function ". Further, since the multi-beam scanning device of the present invention uses the above-described scanning and imaging optical system,
Scanning line bending inherent in the multi-beam scanning device can be corrected and reduced extremely favorably, and good multi-beam scanning can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of a multi-beam scanning device according to the present invention.

FIG. 2 is a diagram for explaining a scan line curve inherent to two beams and an effect of correcting the scan line curve in the embodiment.

FIG. 3 is a diagram illustrating fθ characteristics, which are constant velocity characteristics of the example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Light source (semiconductor laser array) 101,102 Light-emitting part 15 Collimating lens 25 Cylindrical lens 30 Optical deflector (polygon mirror) 41,42,43 Lens which comprises a scanning imaging optical system 50 Scanning surface

Claims (9)

[Claims] An optical deflector deflects a plurality of beams from a light source having a plurality of light emitting portions deflected to one side of an optical axis in at least a direction corresponding to a sub-scanning direction, and scans the plurality of beams on a surface to be scanned by a scanning image forming optical system. A scanning image forming optical system of a multi-beam scanning device that collects light as a plurality of light spots separated in the sub-scanning corresponding direction and optically scans a plurality of lines at the same time, and corrects a scan line bending inherent to the multi-beam scanning device. A correction surface having a refraction surface, and an inclination of the correction refraction surface in a sub-scan section at an incident position of at least one beam among the plurality of beams incident on the correction refraction surface corrects the scan line bending of the beam. As described above, the scanning image forming optical system of the multi-beam scanning device is determined according to the incident position. 2. The scanning image forming optical system according to claim 1, wherein the scanning image forming optical system includes two lenses provided between the optical deflector and the surface to be scanned. A single long lens provided closer to the surface to be scanned than the two lenses,
A scanning image forming optical system of a multi-beam scanning device having a function of converging a deflected beam as a light spot on a surface to be scanned. 3. A scanning image forming optical system of a multi-beam scanning apparatus according to claim 2, wherein one surface of the long lens is a correction refractive surface, and a center of curvature in a sub-scan section of the correction refractive surface is main-scanned. A scanning imaging optical system of a multi-beam scanning device, wherein a center line of curvature connected to a corresponding direction is a three-dimensional curve. 4. A scanning image forming optical system of a multi-beam scanning apparatus according to claim 1, wherein the light deflector deflects at a constant angular velocity so as to make optical scanning at a constant speed. A scanning image forming optical system for a multi-beam scanning device, comprising: 5. A scanning image forming optical system for a multi-beam scanning apparatus according to claim 1, wherein the vicinity of the starting point of deflection by the optical deflector and the position of the surface to be scanned are defined with respect to the sub-scanning corresponding direction. A scanning imaging optical system of a multi-beam scanning device, which has a function of establishing a geometric conjugate relationship. 6. A beam deflector deflects a plurality of beams from a light source having a plurality of light emitting portions deflected to one side of an optical axis in at least a direction corresponding to the sub-scanning direction, and scans the plurality of beams onto a surface to be scanned by a scanning image forming optical system. A multi-beam scanning device that converges as a plurality of light spots separated in a sub-scanning corresponding direction and optically scans a plurality of lines at the same time, wherein the scanning image forming optical system is any one of claims 1 to 5. A multi-beam scanning device using a scanning imaging optical system. 7. A plurality of beams from a light source having a plurality of light-emitting portions deflected to one side of the optical axis at least in a direction corresponding to the sub-scanning direction are deflected at an equal angular velocity by an optical deflector, and are scanned by a scanning image forming optical system. 5. A multi-beam scanning device for converging a plurality of light spots on a scanning surface in a direction corresponding to sub-scanning and simultaneously optically scanning a plurality of lines, wherein the scanning image forming optical system is used as a scanning image forming optical system. A multi-beam scanning device using an optical system. 8. A plurality of beams from a light source having a plurality of light emitting portions deflected to one side of the optical axis in at least a direction corresponding to the sub-scanning direction, and a plurality of beams long in the main scanning corresponding direction near the deflecting reflection surface of the optical deflector. It is formed as a linear image, deflected at the same angular velocity by the optical deflector, and condensed as a plurality of light spots separated in the sub-scanning corresponding direction on the surface to be scanned by the scanning image forming optical system, and a plurality of lines are simultaneously formed. A multi-beam scanning apparatus for performing optical scanning, wherein the scanning image forming optical system according to claim 5, wherein the optical deflector deflects at a constant angular velocity the light scanning by a plurality of beams. A multi-beam scanning device characterized by using a device having a function. 9. The multi-beam scanning device according to claim 6, wherein the light source has two light-emitting portions.