JP2003177345A - Light beam scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent color slurring from occurring on the synthetic image of a latent image by scanning due to the thermal expansion of an optical device caused by a situation that scanning directions on a photoreceptor are opposite among respective light beams in a light beam scanner equipped with a plurality of image forming optical systems to perform scanning with a plurality of light beams by a deflection means having a plurality of deflection surfaces on the single photoreceptor. <P>SOLUTION: By arranging a 1st image forming optical system 20-1 scanning the photoreceptor 4 with the 1st beam B1' being a plurality of light beams, and a 2nd image forming optical system 20-2 scanning the photoreceptor 4 with a 2nd beam B2' on the same side as a polygon scanner 10b, the 1st beam B1' and the 2nd beam B2' are made to scan in the same direction. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning device used in an image forming apparatus such as a copying machine, a printer or a facsimile, which scans and develops a plurality of light beams to obtain a color image.

[0002]

2. Description of the Related Art A light beam scanning device having a plurality of imaging optical systems for scanning a single or a plurality of photoconductors with a plurality of light beams having a laser diode as a light source, and the scanning of the light beam scanning device is provided. The latent image obtained on the photoconductor by the above is visualized, and these visible images are superposed and transferred onto a sheet medium (hereinafter referred to as transfer paper) to obtain a multicolor image. As a multicolor image forming apparatus for fixing and outputting an image, various types are known as shown in FIGS.

[Type 1] FIG. 5 shows a configuration in which the light beam scanning device is applied to a light beam scanning device of a digital color printer. In FIG. 5, reference numeral 1 indicates a polygon scanner. Reference numeral 2-1 indicates a first image forming optical system, and fθ lenses 5-1 and 6-1 and a toroidal lens 7-
1 and folding mirrors 3-1a and 3-1b. Reference numeral 2-2 indicates a second image forming optical system, and the fθ lens 5-2,
6-2, toroidal lens 7-2, folding mirror 3-
2a, 3-2b, etc. Reference numeral 4 denotes a drum-shaped photoconductor.

The polygon scanner 1 and the first in FIG.
The folding mirrors 3-1a, 3-1b, 3-1b,
FIG. 6 shows an optically equivalent positional relationship excluding 3-2a and 3-2b.

In FIG. 6, assuming that the polygon scanner 1 rotates in the direction of the arrow, the first imaging optical system 2-
1 has a synchronization detection unit 15-1 at the scanning start end, and 1
Uses a point synchronization detection method. Further, the second imaging optical system 2-2 adopts the one-point synchronization system in which the synchronization detection unit 15-3 is arranged at the scanning start end.

In FIG. 6, one side of the polygon scanner 1 is provided with a first laser light emitting device 11 and a second laser light emitting device 12 which are LDs (laser diodes) for irradiating laser beams on different mirror surfaces of the polygon scanner 1. Are arranged.

The polygon scanner 1 scans a light beam emitted from a first laser light emitting device 11, a second laser light emitting device 12 or the like as a light source unit on a photoconductor 4 in a main scanning direction (axial longitudinal direction of the photoconductor). It rotates in such a direction (main scanning direction). The photoconductor 4 rotates in the sub-scanning direction orthogonal to the main scanning direction.

The first laser light emitting device 11 and the second laser light emitting device 12 are driven based on image data input by an image data input device (not shown). In the light beam scanning device 2 including the first image forming optical system 2-1, the second image forming optical system 2-2, the polygon scanner 1 and the like, in FIG. 5 and FIG. 6, the light is emitted from the first laser light emitting device 11. The first beam B1 passes through the cylindrical lens 13, is reflected by the polygon scanner 1, and is reflected by the fθ lens 5-
1 and 6-1 and then folded back by the folding mirror 3-1a, passing through the toroidal lens 7-1 and folding mirror 3
-1b, as shown in FIG. 5, the irradiation position A on the photoconductor 4 (starting from the front side in the direction of penetrating the plane of FIG. 5) main scanning direction (direction of penetrating the plane of FIG. 5)
Scan toward the back.

On the other hand, the second beam B2 emitted from the second laser light emitting device 12 passes through the cylindrical lens 14, is reflected by the polygon scanner 1, passes through the fθ lenses 5-2 and 6-2, and is then a folding mirror. 3-2a, passes through the toroidal lens 7-2, is folded by the folding mirror 3-2b, and is irradiated at the irradiation position B of the photoconductor 4 as shown in FIG. 5 (the back side in the direction of penetrating the paper surface in FIG. 5). Scanning is performed toward the front side in the main scanning direction (a direction passing through the paper surface in FIG. 5) (as a base point).

Since the first beam B1 and the second beam B2 are reflected by different mirror surfaces on opposite sides of the rotation center of the polygon scanner 1, the first beam B1 and the second beam B2 are reflected on the photosensitive member 4 according to the rotation of the polygon scanner 1. Thus, scanning is performed in the opposite directions in the main scanning direction.

As described above, the first laser emission device 11,
The first beam B1 and the second beam B2 emitted from the two light emitting sources of the second laser light emitting device 12 are simultaneously swung in the main scanning direction by the polygon scanner 1 while the photosensitive member 4 rotating in the sub scanning direction is rotated. By exposing the surface to a light beam, electrostatic latent images are formed at different positions on the surface of the photoconductor 4.

Next, toner particles of different colors are made to adhere to the electrostatic latent images formed at these different positions on the surface of the photoconductor 4 by developing devices 9 and 10 to form a toner image. The toner images are visualized and superposed and transferred onto a transfer paper (not shown) by the action of a transfer charger (not shown).

The transfer sheet after transfer thus transferred is fed toward the sheet discharge section side by the conveyor belt 110 as shown by the arrow, and heat and pressure are applied by the fixing device 16 to form a toner image on the transfer sheet surface. A multicolor image is obtained on the transfer paper by fixing the image on the transfer paper. In FIG. 5, reference numeral 8 is a charger for uniformly charging the surface of the photoconductor 4 before exposure scanning with a light beam, and reference numeral 120 is the photoconductor 4 after transfer.
The cleaning units for removing and recovering the residual toner remaining on the surface of are shown respectively.

[Type 2] FIG. 7 shows an outline of a multicolor image forming apparatus of type 2. In this type 2 multicolor image forming apparatus, the basic configuration of the imaging optical system is such that the light beams of the two reflected lights from one polygon scanner are guided to the two photoconductors. By providing two combinations of two photoconductors combined with the light beam scanning device including one polygon mirror and two imaging optical systems, toner images of different colors are formed on the four photoconductors. , Overlay transfer on transfer paper.

Here, the polygon scanner 1 according to the type 1 shown in FIGS. 5 and 6, the first image forming optical system 2-1,
The light beam scanning device and the photoconductor 4 by the second image forming optical system 2-2 are the polygon scanner 1a, the first image forming optical system 2-1a, and the second image forming device in the multicolor image forming apparatus in FIG.
The light beam scanning device by the imaging optical system 2-2a and the photoconductors 4a1 and 4a2 correspond to each other. Furthermore, a polygon scanner 1 having exactly the same configuration as this light beam scanning device
a ′, first imaging optical system 2-1a ′, second imaging optical system 2-2
a ′ and the photoconductors 4a1 ′ and 4a2 ′ are arranged side by side to form a multicolor image forming apparatus.

In this multi-color image forming apparatus, the toner images of different colors formed on the photoconductors 4a2 ', 4a1', 4a2, 4a1 are sequentially transferred onto the transfer paper moving in the arrow direction in the order of the photoconductors. Overprint transfer to obtain a full-color image.

[Type 3] FIG. 8 shows an outline of a multicolor image forming apparatus according to Type 3. In this type 3 multi-color image forming apparatus, the polygon scanner is coaxial
It is composed of a stepped polygon mirror, and the light beams of two reflected lights from one polygon mirror are guided to two photoconductors. The light beam scanning device having one polygon mirror and two image forming optical systems is provided with two structures in which two photoconductors are combined, and toner images of different colors are formed on the four photoconductors thus arranged. , Overlay transfer on transfer paper.

Here, the polygon scanner 1 and the first image forming optical system 2-1 shown in FIGS.
The second imaging optical system 2-2 and the photoconductor 4 are the polygon mirror 1b1 and the photoconductor 4 in the multicolor image forming apparatus in FIG.
First imaging optical system 2-1b1, second imaging optical system 2-2b
1 corresponds to the photoconductors 4b1 and 4b2.

Then, the polygon mirror 1 having exactly the same structure
b1 ′, the first image forming optical system 2-1b1 ′, the second image forming optical system 2-2b1 ′, and the photoconductors 4b1 ′ and 4b2 ′ are stacked to form a multicolor image forming apparatus. The polygon mirrors 1b1 and 1b1 'form part of a two-stage polygon scanner 1b.

In this multi-color image forming apparatus, the toner images of different colors formed on the photoconductors 4b2 ', 4b2, 4b1 and 4b1' are transferred onto the transfer paper S moving in the arrow direction in the order of the photoconductors. A full-color image is obtained by sequentially transferring the images.

[Type 4] FIG. 9 shows an outline of a multicolor image forming apparatus according to Type 4. In this type 4 multicolor image forming apparatus, the basic configuration of the imaging optical system is the same as that of type 1. The difference is that for each photoconductor, two sets of light beam scanning devices consisting of one polygon scanner and two imaging optical systems are provided, and four photoimages of different colors are formed on this one photoconductor. This is the point of overlapping transfer on the transfer paper.

Here, the polygon scanner 1 and the first image forming optical system 2-1 shown in FIGS.
The second imaging optical system 2-2 and the photoconductor 4 are the same as those of the polygon scanner 1 in the multicolor image forming apparatus in FIG.
c, the first imaging optical system 2-1c, the second imaging optical system 2-2
c and the photoconductor 4c correspond to each other.

The polygon scanner 1 having the same structure
c ′, first imaging optical system 2-1c ′, second imaging optical system 2-2
An image forming apparatus for multicolor is configured by arranging c ′ and the like in parallel. In this multi-color image forming apparatus, toner images of different colors formed on the photoconductor 4c are sequentially superimposed and transferred onto a transfer paper (not shown) that moves in contact with the photoconductor 4c to obtain a full-color image.

The light beam scanning device according to the combination of the image forming optical systems and the polygon scanner in the image forming apparatus for each of the three types of types 2 to 4 has a slight difference in the configuration. Even if there is,
As with the light beam scanning device in the type 1 multicolor image forming apparatus shown in FIG. 6, color shift occurs due to thermal expansion of the optical housing.

That is, in a laser printer or a digital image forming apparatus having such a light beam scanning device, a relative position change between the photoconductor and the light beam scanning device is caused by a temperature change inside the image forming device. The relative position of the laser light source (not shown) that irradiates the polygon scanner with the light beam and the polygon mirror, the fθ lens, and the folding mirror changes, and the irradiation position of the light beam on the photoconductor changes. A color shift occurs due to the position shift of the image.

Such a problem is caused by the problems of JP-A-6-1002, JP-A-63-30025 and JP-A-1-14.
It is considered that the same phenomenon occurs in the image forming apparatus described in Japanese Patent No. 1746, etc., which is one of the causes of the color misregistration.

Conventionally, an optical sensor or a CCD (charge coupled)
These irradiation positions A and B using an imaging device)
A method has been adopted in which the deviation amount is detected and the writing timing of the image signal is controlled according to the deviation amount to correct the deviation.

However, according to these methods, an optical sensor, a CCD, a control circuit for changing the timing of this detection circuit and a signal, and the like are required, resulting in a complicated structure and an obstacle to cost reduction.

If there are a plurality of photoconductors, color misregistration also occurs due to each mounting error. When aiming for high image quality, it is necessary to dramatically reduce this mounting error.
Therefore, it is preferable that the number of the photoconductors is one.

[0030]

SUMMARY OF THE INVENTION An object of the present invention is to suppress color misregistration of a color image due to a difference in the direction of deviation and the amount of deviation of the irradiation positions A and B of the light beam, which are caused by temperature fluctuations. It is to solve the problem of color misregistration at a cost.

[0031]

The present invention has the following constitution in order to achieve the above object. (1). A light beam scanning device having a plurality of imaging optical systems for scanning a single photoconductor with a plurality of light beams by a deflection means having a plurality of deflection surfaces, wherein a plurality of light beams for scanning the photoconductor are provided. The beam scanning directions are all the same (claim 1). (2). (1) In the light beam scanning device described in 1,
The deflecting unit is configured by stacking polygon mirrors having a plurality of deflecting surfaces in multiple stages, and some of the optical elements that form the imaging optical system are configured by stacking the same molded product in multiple stages. The optical element described above or a single optical element having a structure in which the same optical element is stacked in a plurality of stages (claim 2). (3). In the light beam device according to (2), the optical element is a resin molded product (claim 3). (4). In the light beam scanning device according to any one of (1) to (3), each optical element included in the imaging optical system forming at least one writing system is attached from the same direction in the main scanning direction. It was decided to be applied and positioned (Claim 4). (5). In the light beam scanning device according to any one of (1) to (4), at least one writing system includes a light source unit capable of emitting two or more light beams. (Claim 5). (6). The latent image obtained on the photoconductor by the scanning of the light beam is made into a visible image, and these visible images are superposed and transferred onto the sheet-like medium to obtain a multicolor image, and this multicolor image is fixed. In the image forming apparatus for outputting, the light beam scanning device according to any one of claims 1 to 5 is provided as means for scanning the photoconductor (claim 6).

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a light beam scanning device according to the present invention. As a deflecting means having a plurality of deflecting surfaces, polygon mirrors 10b1 and 10b stacked in two stages are used.
The polygon scanner 10b consisting of 1'is attached to the mount 60.
Fixed on the same side as the polygon scanner, a first imaging optical system 20-1 and a second imaging optical system 20-2 are provided on the same side.
Are arranged.

The second polygon mirror 10b1 'in the lower stage has a second
The fθ lens 50-2, which is part of the optical element in the imaging optical system 20-2, and the fθ lens 60-2, which is part of the optical element in the second imaging optical system 20-2, are each optically. Correspondingly, it is fixed to the mounting base 60. Then, the f.theta. Lens 50-1 which is a part of the optical element in the first imaging optical system 20-1 is superposed on the f.theta. Is optically compatible with.

Further, the fθ lens 60-2 is formed by stacking the fθ lens 60-1 which is a part of the optical element in the first imaging optical system 20-1 on the fθ lens 60-2 to form two stages.
It corresponds to -1 optically. Here, “corresponding optically” means a relationship in which a light beam emitted from one side can be incident on the other side.

Thus, specifically, the fθ lens 50-
Fθ lens 50-2 is stacked in two stages on top of 1, and
The fθ lens 60-2 is stacked in two stages on the fθ lens 60-1.

The upper and lower fθ lenses may be fixed to each other or an adhesive between them, or may be fixed by pressing integrally with a leaf spring or the like. Whatever it is,
The fθ lenses 50-1 and 50-2 are integrally formed, and the fθ lenses 60-1 and 60-2 are also integrally formed.
b is attached to a common mount 60.

In this example, the fθ lens 50-2 and fθ lens
The lens 50-1, the fθ lens 60-2, and the fθ lens 6
Two identical optical elements that are independent of each other are used as 0-1 and two identical optical elements are simply stacked to form a two-stage configuration and integrally fixed to obtain a required configuration.

In the above example, the fθ lens 50-1 is overlaid on the fθ lens 50-2, and the fθ lens 60-2 is used.
Although the imaging optical system is composed of optical elements formed by stacking the same molded product in a plurality of stages such as stacking the fθ lens 60-1 on the above, it is possible to form it as a single optical element. is there. By doing so, handling is facilitated in that no means for integrally fixing the two optical elements is required, and there is no deviation between the two optical elements, and
Assembling becomes easier and cost can be reduced.

In this example, the example of two stages has been described, but the number of stages is not limited to two, and it is also possible to have a plurality of stages in accordance with a plurality of stages of polygon mirrors. Further, in any of these examples, when the optical element is a resin molded product, the optical element can be easily molded, and high-precision optical elements can be mass-produced.

Regarding the first imaging optical system 20-1, for example, the beam emitted from the light source unit 11'-1 according to the first laser light emitting device 11 shown in FIG. 6 is reflected by the polygon mirror 10b1. fθ lens 50-1, 60-
1, the folding mirrors 3-1a and 3-1b, the toroidal lens 7-1, and the folding mirror 3-1c, and the main scanning direction (see FIG. Scanning toward the back side in the direction of penetrating the paper surface).

Regarding the second image-forming optical system 20-2, the beam emitted from the light source unit 11'-2 according to the light source unit 11'-1 is reflected by the polygon mirror 10b1 'and the fθ lens 50-2, 60-2, folding mirrors 3-2a, 3-
2b, through the toroidal lens 7-2, scanning is performed toward the back side in the main scanning direction (direction penetrating the paper surface in FIG. 4) with the irradiation position B ′ (front side of the paper surface penetrating in FIG. 4) as a base point.

Now, the difference in the positional deviation of the light beam between the conventional example (FIGS. 5 to 8) and this example (FIG. 1) when the temperature fluctuation occurs will be described. In the case of the conventional example, for example, when temperature fluctuations occur in FIG. 5 and each optical element forming the first imaging optical system 2-1 thermally expands, the first beam B1 ′ shifts in the main scanning direction and the photoconductor 4 is moved. Irradiate the top.

On the other hand, for the second imaging optical system 2-2,
Since the optical elements are arranged point-symmetrically with respect to the first imaging optical system 2-1 and the polygon scanner 1, the direction of thermal expansion is opposite to that of the first imaging optical system 2-1. Therefore, the second beam B2 ′ is shifted in the direction opposite to the first beam B1 ′ in the main scanning direction and irradiates the photosensitive member 4 with the light beam. Therefore, the actual amount of misalignment is doubled, which causes color misregistration.

However, as shown in FIG. 1, by disposing the first image forming optical system 20-1 and the second image forming optical system 20-2 on the same side with respect to the polygon scanner 10, the photosensitive member 4 The scanning directions of the first beam B1 ′ and the second beam B2 ′ that scan upward are all the same.

With this configuration, the directions of thermal expansion of the first image forming optical system 20-1 and the second image forming optical system 20-2 are the same even if there is a temperature change. The deviation of the scanning position of the light beam in the main scanning direction is also in the same direction, and the color deviation hardly occurs.

Further, comparing with the conventional example of FIG. 5,
Since the first image forming optical system 20-1 and the second image forming optical system 20-2 are fixed and held on a common optical housing (not shown), they are hardly affected by them, which is more than the conventional example. Excellent in that there is no color shift.

As described with reference to FIG. 1, the fθ lens 50-
1, 50-2 are integrally configured, and the fθ lens 60-
1, 60-2 are also integrally configured. Then, as shown in FIG. 2, the fθ lens 50 in the main scanning direction is
-1, 50-2 each longitudinal end of the stationary member, for example,
The common abutting member 20 fixed to the mounting base 60 is applied and held in position.

Similarly, the longitudinal end portions of the fθ lenses 60-1 and 60-2 in the main scanning direction are held against the common abutting member 30 fixed to the immovable member. These abutting members 20 and 30 are respectively provided on the same side in the main scanning corresponding direction so that the influence of thermal expansion is exerted on the group of fθ lenses 50-1 and 50-2 and the fθ lens 60-1.
The 60-2 group extends in the same direction.

Further, in order to ensure the contact with the contact members 20, 30, the contact members 20, 30,
From the opposite side of 30, elastic means 20SP, 30SP such as springs
Is pressed by.

Further, in order to stabilize the installation position of the group of fθ lenses 50-1 and 50-2, these fθ lenses 50- are attached to the abutting member 40 fixed to the immovable member in the direction orthogonal to the main scanning direction. 1, 50-2
Is pressed by an elastic means 40SP such as a spring to hold the position.

Similarly, in order to stabilize the installation position of the group of fθ lenses 60-1 and 60-2, these fθ lenses 60 are attached to the abutting member 50 fixed to the immovable member in the direction orthogonal to the main scanning direction. -1, 60-2
Is pressed by an elastic means 50SP such as a spring to hold the position.

As described above, in the main scanning direction, the groups of the respective fθ lenses are positioned by abutting against the abutting members 20 and 30, so that the expansion directions of the respective optical elements are in the same direction even if the temperature varies. There is no relative difference in irradiation position. Therefore, by doing so, it is possible to suppress the contribution that affects the light beam on the surface to be scanned to a small level. In FIG. 2, the symbol O indicates the polygon mirror 1.
The rotation centers of 0b1 and 10b1 'are shown, and the displacement of the reflecting surface due to the rotation is shown by a solid line and a two-dot chain line, respectively.

In the above examples, each light beam scanning device has been described as a single laser diode having a single light source, but it can be configured to have a light source section capable of emitting two or more light beams. .

In this case, the light source unit may be a multi-laser diode having a plurality of light sources, or a light source unit composed of a plurality of single laser diodes combined by a combining prism or the like. An example of a light source unit that emits two light beams by using two single laser diodes will be described with reference to FIG.

In FIG. 3, the light source section includes a first laser diode LD1, a second laser diode LD2, a first collimating lens L1 and a second collimating lens L.
It has a half-wave plate L3, a reflecting surface L4, a polarization beam splitter L5, and the like.

The light beam emitted from the first laser diode LD1 is converted into parallel light by the first collimator lens L1 and transmitted through the polarization beam splitter L5. The light beam emitted from the second laser diode LD2 is converted into parallel light by the second collimator lens L2, the polarization plane is rotated by the ½ wavelength plate L3, and the light is deflected in the order of the reflection surface L4 and the polarization beam splitter L5. Then, the light beam is emitted in a direction opened by a predetermined angle in a predetermined direction with respect to the light beam. Thus, one light source unit 61
And two light beams are emitted.

Two light source units having the same structure as the light source unit 61 thus configured are prepared, one of the light source units is made incident on the polygon mirror 10b1 in FIG. 1, and the other light source unit is arranged as shown in FIG. Polygon mirror 10b1 'in
When the light beam is incident on the photoconductor, all the multi-beams can be scanned on the photoconductor in the same scanning direction, and the speed can be further increased.

An example in which the light beam scanning device shown in FIG. 1 is mounted on a color image forming apparatus is shown in FIG. In FIG. 4, the same reference numerals as those in FIG. 5 are attached to the components common to the configuration already described in FIG.

Light source units 11'-1 and 11'-2 are arranged on the same side of the polygon scanner 10b. The surface of the photoconductor 4 is previously uniformly charged by the charger 8 before being exposed and scanned by the light beam.

The first beam B1 'emitted from the light source unit 11'-1 is reflected by the polygon mirror 10b1 and then
Fθ lens 50-constituting the first imaging optical system 20-1
1, 60-1, the folding mirrors 3-1a and 3-1b, the toroidal lens 7-1, and the folding mirror 3-1c through the irradiation position A '(the front side in the direction of penetrating the paper surface in FIG. 5).
The scanning is performed toward the back side in the main scanning direction (direction penetrating the paper surface in FIG. 1) with the base point as the base point.

Similarly, the second beam B2 'emitted from the light source unit 11'-2 is reflected by the polygon mirror 10b1' and then on the same side as the first imaging optical system 20-1 with respect to the polygon mirror 10b. Second imaging optical system 20-2 arranged at
Via the fθ lenses 50-2 and 60-2, the folding mirrors 3-2a and 3-2b, and the toroidal lens 7-2 that constitute the The scanning is performed toward the back side in the scanning direction (the direction passing through the paper surface in FIG. 1).

Next, the first beam B on the surface of the photoconductor 4
The electrostatic latent image by the scanning of 1'is visualized by the developing device 9, and the electrostatic latent image by the scanning of the second beam B2 'is visualized by the toner particles of different colors by the developing device 10. A transfer charger (not shown) works to superimpose and transfer it onto a transfer paper (not shown).

The transfer sheet after the transfer thus transferred is fed toward the sheet discharge section side by the conveyor belt 110 as shown by an arrow, and the fixing device 16 applies heat and pressure to the toner image on the transfer sheet surface. A multicolor image is obtained on the transfer paper by fixing the image on the transfer paper. The residual toner remaining on the surface of the photoconductor 4 after the transfer is removed and collected by the cleaning unit 120.

In the present example, the light beam scanning device having two stacked layers has been described, but the same applies to the light beam scanning device having four stacked layers in order to develop into a full-color image forming apparatus of four colors. Needless to say.

[0065]

According to the first aspect of the invention, since the directions of scanning by the plurality of light beams for scanning the photoconductor are all the same, the direction of deviation of the irradiation position of the light beam caused by the temperature fluctuation is The color misregistration of the color image due to the difference in the amount of misregistration can be suppressed, and the problem of color misregistration can be solved at low cost.

According to the second aspect of the invention, a plurality of optical elements can be easily constructed. According to the third aspect of the invention, since the optical element is a resin molded product, the optical element can be easily molded, and high-precision optical elements can be mass-produced.

According to the fourth aspect of the invention, the directions of expansion of the optical elements are the same, and there is no relative difference in irradiation position.

According to the fifth aspect of the present invention, a high writing speed can be realized by forming the multi-beam writing system while eliminating the color shift. According to the invention of claim 6, it is possible to provide a color image forming apparatus having no color shift.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a main part of a light beam scanning device according to the present invention.

FIG. 2 is a plan view illustrating the arrangement of optical elements according to the present invention in relation to a polygon mirror.

FIG. 3 is a perspective view illustrating a configuration example of a light source unit that emits multi-beams.

FIG. 4 is a diagram illustrating an overall configuration of an image forming apparatus according to the present invention.

FIG. 5 is a diagram illustrating an arrangement of an image forming optical system in an image forming apparatus according to a conventional technique.

FIG. 6 is a diagram illustrating an arrangement of an image forming optical system in an image forming apparatus according to a conventional technique.

FIG. 7 is a diagram illustrating an arrangement of an image forming optical system in an image forming apparatus according to a conventional technique.

FIG. 8 is a diagram illustrating an arrangement of an image forming optical system in an image forming apparatus according to a conventional technique.

FIG. 9 is a diagram illustrating an arrangement of an image forming optical system in an image forming apparatus according to a conventional technique.

[Explanation of symbols]

10b polygon scanner 20-1 First Imaging Optical System 20-2 Second imaging optical system

Claims (6)

[Claims] 1. A light beam scanning device comprising a plurality of image forming optical systems for scanning a single photosensitive member with a plurality of light beams by a deflecting means having a plurality of deflecting surfaces. A light beam scanning device characterized in that the scanning directions of a plurality of scanning light beams are all the same. 2. The light beam scanning device according to claim 1, wherein the deflecting unit is configured by stacking a plurality of polygon mirrors having a plurality of deflecting surfaces in a plurality of stages to configure the image forming optical system. The optical element of the part is a light beam characterized by comprising an optical element formed by stacking the same molded product in multiple stages or a single optical element formed by a structure in which the same optical element is stacked in multiple stages. Scanning device. 3. The light beam scanning device according to claim 2, wherein the optical element is a resin molded product. 4. The light beam scanning device according to claim 1, wherein at least one optical element included in the imaging optical system constituting the writing system is the same in the main scanning direction. A light beam scanning device characterized in that it is abutted from a direction and positioned. 5. The light beam scanning device according to claim 1, wherein at least one writing system includes a light source unit capable of emitting two or more light beams. A light beam scanning device comprising a writing system. 6. An electrostatic latent image obtained on a photoconductor by scanning with a light beam is visualized, and these visible images are superposed and transferred onto a sheet-like medium to obtain a multicolor image. An image forming apparatus for fixing and outputting a multicolor image, comprising the light beam scanning device according to claim 1 as means for scanning the photoconductor.