JP2003270570A - Multibeam scanning optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact multibeam scanning optical system which eliminates the need for complicated initial adjustments and seldom causes color slurring. <P>SOLUTION: The multibeam scanning optical system which guides four laser beams (LY, LM, LC, and LK) deflected by a deflecting and reflecting surface (1S) of a polygon mirror (1) divisionally to four photosensitive drums (9Y, 9M, 9C, and 9K) to image them on the photosensitive drums (9Y, 9M, 9C, and 9K) is equipped with a polyhedral long-sized mirror (J1) which reflects the four laser beams (LY, LM, LC, and LK) in mutually different directions by four reflecting surfaces which are adjacent at mutually different angles. <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 multi-beam scanning optical system, for example, a color image forming apparatus.
A tandem-type multi-beam scanning optical system for exposing and recording an image on each of a plurality of photoconductors by deflectively scanning a plurality of beams or a beam group in a print head of a color laser beam printer, a color digital copying machine, etc. It is about.

[0002]

2. Description of the Related Art In a digital PPC (Plain Paper Copier) or a laser beam printer, a tandem color developing method is known in which a plurality of photosensitive drums are used to sequentially develop a plurality of colors in order to increase a color image output speed. ing. When this method is adopted, normally, a semiconductor laser or an LED (Light) is provided for each of the four photoconductor drums corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K). Exposure and development according to the image of each color are performed by the Emitting Diode) array. Therefore, it is important to reduce the image position shift (that is, color shift) between the color images in the color image output while reducing the apparatus volume as much as possible.

As a tandem type multi-beam scanning optical system, there is known a type in which an image is exposed and recorded on each photosensitive drum by deflecting and scanning a plurality of (for example, YMCK) laser beams on the same surface of a deflector. . In order to avoid increasing the size of the deflector in this type, it is necessary to combine the optical paths before entering the deflector and separate the spatial optical paths after exiting the deflector (so-called combining / separation method). Therefore, generally, a plurality of laser beams are configured to enter the same surface of the deflector at different angles in the sub-scanning direction. Each laser beam separated in the sub-scanning direction by the deflector is further separated in optical path by an individual long mirror corresponding to each color, and is guided to each photoconductor drum (Japanese Patent Laid-Open No. 8-
271817, JP-A-11-95140, JP-A-1
1-194285, JP-A-11-119131, etc.).

[0004]

However, in the conventional multi-beam scanning optical system (JP-A-8-271817, etc.),
A large space is required to arrange each long mirror. Further, at the time of initial adjustment of each beam scanning position (for example, adjustment of relative position / relative angle of each laser beam), very complicated adjustment is required in each long mirror,
Adjustment time is long and cost is high. Moreover, since it is necessary to separately secure a space for adjusting the long mirror, the entire scanning device becomes large. Further, there is also a problem that each beam scanning position is likely to change (that is, a color shift is likely to occur) due to environmental changes (changes in temperature and humidity) and changes over time. If a special sensor for correcting each beam scanning position is used in order to prevent the deviation of the initial setting value of the optical system due to environmental changes or changes over time (for example, Japanese Patent Laid-Open No. 10-148775), the cost is further increased. It gets expensive.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a compact multi-beam scanning optical system in which complicated initial adjustment is unnecessary and color misregistration does not easily occur. .

[0006]

In order to achieve the above object, the multi-beam scanning optical system according to the first aspect of the present invention divides a plurality of deflected beams or beam groups into a plurality of photoconductors and guides them. A multi-beam scanning optical system for imaging and scanning the above, comprising a multi-faced elongated mirror for reflecting a plurality of beams or beam groups in different directions by a plurality of reflecting surfaces.

The multi-beam scanning optical system of the second invention is
In the configuration of the first aspect of the invention, the positions and angles of a plurality of beams or beam groups are integrally adjusted by adjusting the positions and angles of the multifaceted long mirror.

The multi-beam scanning optical system of the third invention is
In the configuration of the first or second aspect of the invention, the plurality of beams or beam groups are reflected only on the reflecting surface of the multifaceted long mirror.

The multi-beam scanning optical system of the fourth invention is
In the structure of the first, second or third invention, the multifaceted long mirror is made of resin.

The multi-beam scanning optical system of the fifth invention is
In the structure of the first, second, third or fourth invention,
The beam group is composed of a plurality of beams parallel to each other.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multi-beam scanning optical system embodying the present invention will be described below with reference to the drawings. Figure 1
FIG. 6 shows the first to sixth embodiments of the tandem-type multi-beam scanning optical system in sub-scan section. See also FIG.
The standard configuration of the tandem type multi-beam scanning optical system is shown in a sub-scan section as a reference example. 1 to 7, 1 is a polygon mirror (deflector) that performs deflection scanning by rotation, 1S
Is a deflecting / reflecting surface (deflecting surface consisting of a mirror surface), ax is a rotation axis of the polygon mirror (1), 2 is a polygon window, and 3 and 4 are f.
θ lens, H, H1, H2, H5, H6 are housings, LY, LM, LC, LK are laser beams corresponding to each color of YMCK, AX is optical axis of fθ lens (3, 4), 5Y, 5M, 5C , 5K; 6M, 6C, 6K; 15; 16Y, 16M, 16
C, 16K is a reflection mirror, 7Y, 7M, 7C, 7K is a long lens, 8Y, 8M,
8C and 8K are print head windows, 9Y, 9M, 9C and 9K are photosensitive drums, and J1, J2, J3, J4, J5 and J6 are resin multi-faceted long mirrors. The main scanning direction is the laser beam (LY, LM, LC,
LK) is a direction in which each photoconductor drum (9Y, 9M, 9C, 9K) is scanned by being deflected by the deflection reflection surface (1S), and the sub-scanning direction is a direction perpendicular to the main scanning direction.

First, a reference example of the multi-beam scanning optical system shown in FIG. 7 will be described. This multi-beam scanning optical system
Housing (H) except for the photoconductor drums (9Y, 9M, 9C, 9K)
Mounted in the housing (H) and mounted in the housing (H).
Laser beam (LY, LM, LC, LK) emitted from Y, 8M, 8C, 8K)
Then, four photosensitive drums (9Y, 9Y,
9M, 9C, 9K) image exposure recording at the same time. 4 in the housing (H) (4 in YMCK)
(Color) laser beam (LY, LM, LC, LK) is a polygon mirror
In (1), one deflecting / reflecting surface (1S) at the same position is incident at different angles in the sub-scanning direction, and is deflected and reflected at different angles at the same time. The four deflected and reflected laser beams (LY, LM, LC, LK) pass through the polygon window (2) and the fθ lens (3, 4) while spatially separating the optical paths.

Of the four laser beams (LY, LM, LC, LK) that have passed through the fθ lens (3, 4), the Y laser beam (LY) is long after being reflected by the reflection mirror (5Y). An image is formed on the photosensitive drum (9Y) through the scale lens (7Y) and the print head window (8Y). The laser beam (LM) of M is a reflection mirror (5M, 6
After being reflected by M), the image is formed on the photosensitive drum (9M) through the long lens (7M) and the print head window (8M).
The laser beam (LC) of C is reflected by the reflection mirror (5C, 6C), then the long lens (7C) and the print head window (8C)
An image is formed on the photoconductor drum (9C) through. The K laser beam (LK) is reflected by the reflecting mirrors (5K, 6K), then passes through the long lens (7K) and the print head window (8K) and forms an image on the photosensitive drum (9K). In this way, four laser beams (LY, LM, LC, LK) are used for the four photosensitive drums.
Exposure scanning for (9Y, 9M, 9C, 9K) is performed simultaneously.

In the multi-beam scanning optical system of FIG. 7, fθ
Four laser beams (LY, LM, LC, L that passed through the lens (3, 4)
K) is a reflection mirror (5M, 5C, 5
It will pass through the immediate vicinity of K). At this time, the reflection mirrors (5Y, 5M, 5C, 5K) are arranged at positions far away from the polygon mirror (1) in order to prevent optical path loss. This causes the size of the housing (H) (that is, the printhead size) to increase. This problem is solved by the first to sixth embodiments described below.
(FIGS. 1 to 6).

Also in the first to sixth embodiments (FIGS. 1 to 6),
Similar to the reference example (FIG. 7) described above, four laser beams (LY, four colors of YMCK) deflected by the polygon mirror (1)
(LM, LC, LK) is divided into four photoconductor drums (9Y, 9M, 9C, 9K) and guided, and the image is scanned on each photoconductor drum (9Y, 9M, 9C, 9K). There is. However, by using one multi-faceted long mirror (J1, J2, J3, J4, J5, J6), the optical configuration is greatly different from that of the reference example (FIG. 7). The four laser beams (LY, LM, LC, LK) are laser beams (L1, L1, L3, LC, LK) emitted from a light source unit (30A, 30B, 30C; FIG. 8) described later.
L2, L3, L4) or laser beam group (M1, M2).

The first and second embodiments (FIGS. 1 and 2) are
Similar to the reference example (FIG. 7) described above, the photosensitive drums (9Y, 9M, 9C,
Parts other than (9K) are mounted in the housing (H1, H2) positioned and ejected from the print head windows (8Y, 8M, 8C, 8K) provided in the housing (H1, H2). With the laser beam (LY, LM, LC, LK), exposure recording of images on four photosensitive drums (9Y, 9M, 9C, 9K) corresponding to each color of YMCK is simultaneously performed. Four laser beams (LY, LM, LC, L in the housing (H1, H2)
K) is incident on one deflection reflection surface (1S) at the same position on the polygon mirror (1) at different angles in the sub-scanning direction, and is deflected and reflected at different angles at the same time. The four laser beams (LY, LM, LC, LK) deflected and reflected are spatially separated from each other while the polygon window (2) and f
Passes through the θ lens (3, 4).

The four laser beams (LY, LM, LC, LK) that have passed through the fθ lens (3, 4) are reflected by the reflection mirror (15) and then reflected by the multifaceted long mirrors (J1, J2). Incident. The multi-faceted long mirror (J1, J2) has four plane reflecting surfaces that are adjacent to each other at different angles, and the four plane reflecting surfaces emit four laser beams (LY, LM, LC, LK). Reflect in different directions. In the multifaceted elongated mirror (J1) used in the first embodiment (FIG. 1), four plane reflecting surfaces are convex so as to be adjacent to each other with an angle difference of about 30 °. In addition, the multifaceted long mirror (J2) used in the second embodiment (FIG. 2)
In, the four plane reflecting surfaces are formed in a concave shape so as to be adjacent to each other with an angle difference of about 30 °. Therefore, in the case of the second embodiment, the four laser beams (LY, LM, LC, LK) reflected by the multifaceted long mirror (J2) intersect. The optical axis from the polygon mirror (1) to the multifaceted long mirror (J1, J2)
The distance in the (AX) direction is preferably about the same as the K reflection mirror (5K) in the reference example (FIG. 7). Therefore,
It is desirable that all the laser beams (LY, LM, LC, LK) be folded back by the reflection mirror (15) before the polygonal long mirrors (J1, J2).

Of the four laser beams (LY, LM, LC, LK) reflected by the multifaceted long mirrors (J1, J2), the Y laser beam (LY) was reflected by the reflection mirror (16Y). After the long lens
An image is formed on the photoconductor drum (9Y) through (7Y) and the print head window (8Y). The laser beam (LM) of M is reflected by the reflecting mirror (16M) and then passes through the elongated lens (7M) and the print head window (8M) to form an image on the photosensitive drum (9M). The laser beam (LC) of C is reflected by the reflecting mirror (16C) and then passes through the long lens (7C) and the print head window (8C) to form an image on the photosensitive drum (9C). The K laser beam (LK) is reflected by the reflecting mirror (16K) and then passes through the long lens (7K) and the print head window (8K) to form an image on the photosensitive drum (9K). As described above, 4
The four laser beams (LY, LM, LC, LK) simultaneously perform exposure scanning on the four photoconductor drums (9Y, 9M, 9C, 9K). In the first embodiment, a C reflection mirror (16C)
Are provided, and in the second embodiment, two M reflection mirrors (16M) are provided. By appropriately adding the reflection mirror in this way, the optical configuration can be balanced for each color.

In the first and second embodiments (FIGS. 1 and 2), the bending of the optical path by the reflecting mirrors (16Y, 16M, 16C, 16K) is performed in the same manner as the above-mentioned reference example (FIG. 7). Each photoconductor drum
The emission directions of the laser beams (LY, LM, LC, LK) to (9Y, 9M, 9C, 9K) are the same (that is, parallel to each other). Therefore,
It can be used for a print head of a color image forming apparatus (color laser beam printer, color digital copying machine, etc.) similar to the reference example (FIG. 7). Moreover, the housing (H1, H) in the first and second embodiments (FIGS. 1 and 2) is
Since the size of 2) is smaller than the size of the housing (H) in the reference example (FIG. 7), it is obvious that it can contribute to downsizing of the color image forming apparatus.

In the third and fourth embodiments (FIGS. 3 and 4), the long lenses (7Y, 7M, 7C, 7K) are not provided, and f
It is configured to form an image only with the θ lens (3, 4). Four
The laser beams (LY, LM, LC, LK) of this book are the same as those in the first and second embodiments (FIGS. 1 and 2), and one deflection reflection surface (at the same position on the polygon mirror (1) ( For 1S), they are incident at different angles in the sub-scanning direction and are deflected and reflected at different angles at the same time. Four laser beams (L
(Y, LM, LC, LK) pass through the polygon window (2) and the fθ lens (3, 4) while the optical paths are spatially separated.

The four laser beams (LY, LM, LC, LK) that have passed through the fθ lens (3, 4) are reflected by the reflection mirror (15) and then reflected by the multifaceted long mirror (J3, J4). Incident. The multi-faceted long mirror (J3, J4) has four plane reflecting surfaces adjacent to each other at different angles, and the four plane reflecting surfaces emit four laser beams (LY, LM, LC, LK). Reflect in different directions. In the multifaceted long mirror (J3) used in the third embodiment (FIG. 3), four plane reflecting surfaces are convex so as to be adjacent to each other with an angle difference of about 15 ° (may be about 8 °). I'm in a shape. In addition, in the multifaceted long mirror (J4) used in the fourth embodiment (FIG. 4), four plane reflecting surfaces are about 15
They are formed in a concave shape so that they are adjacent to each other with an angle difference of 8 ° (may be about 8 °). Therefore, in the case of the fourth embodiment,
Four laser beams (LY,
LM, LC, LK) will intersect.

Of the four laser beams (LY, LM, LC, LK) reflected by the multifaceted long mirror (J3, J4), the Y laser beam (LY) was reflected by the reflection mirror (16Y). After that, an image is formed on the photosensitive drum (9Y). The M laser beam (LM) is reflected by the reflection mirror (16M) and then forms an image on the photosensitive drum (9M). The C laser beam (LC) is reflected by the reflecting mirror (16C) and then forms an image on the photosensitive drum (9C). The K laser beam (LK) is reflected by the reflection mirror (16K) and then forms an image on the photosensitive drum (9K). As described above, the four laser beams (LY, LM, LC, LK) allow the four photosensitive drums (9Y, 9Y
Exposure scanning for M, 9C, 9K) is performed simultaneously.

In the third and fourth embodiments (FIGS. 3 and 4), the bending of the optical path by the reflecting mirrors (16Y, 16M, 16C, 16K) causes the same as in the above-described reference example (FIG. 7). Each photoconductor drum
The emission directions of the laser beams (LY, LM, LC, LK) to (9Y, 9M, 9C, 9K) are the same (that is, parallel to each other). Therefore,
It can be used for a print head of a color image forming apparatus (color laser beam printer, color digital copying machine, etc.) similar to the reference example (FIG. 7).

In the fifth and sixth embodiments (FIGS. 5 and 6), the long lenses (7Y, 7M, 7C, 7K) are not provided, and f
It is configured to form an image only with the θ lens (3, 4). In addition, the reflection mirror (15; 16Y, 16M, 16C, 16K) is not provided, and the reflection of the laser beam (LY, LM, LC, LK) is reflected only on the reflection surface of the multifaceted long mirror (J5, J6). Therefore, the emission directions of the laser beams (LY, LM, LC, LK) to the photoconductor drums (9Y, 9M, 9C, 9K) are different (that is, they are not parallel to each other). Four laser beams (LY, LM, LC, LK) in the housing (H5, H6)
However, similar to the first and second embodiments (FIGS. 1 and 2), one deflection reflection surface (1S) at the same position in the polygon mirror (1) is formed at different angles in the sub-scanning direction. The light enters and is deflected and reflected at different angles at the same time. The four laser beams (LY, LM, LC, LK) that have been deflected and reflected are spatially separated in optical path, while the polygon window (2) and the fθ lens are used.
Pass through (3,4).

The four laser beams (LY, LM, LC, LK) that have passed through the fθ lens (3, 4) enter the multifaceted long mirrors (J5, J6). The multifaceted long mirror (J5, J6) has four plane reflecting surfaces adjacent to each other at different angles, and the four plane reflecting surfaces emit four laser beams (LY, LM, LC, LK). Reflect in different directions. In the multifaceted elongated mirror (J5) used in the fifth embodiment (FIG. 5), four plane reflecting surfaces are convex so as to be adjacent to each other with an angle difference of about 15 °. Further, in the multifaceted long mirror (J6) used in the sixth embodiment (FIG. 6), the four plane reflecting surfaces are about 15 °.
The concave shape is formed so that they are adjacent to each other due to the angle difference. Therefore, in the case of the sixth embodiment, the four laser beams (LY, LM, LC, LK) reflected by the multifaceted long mirror (J6) intersect. The four laser beams (LY, LM, LC, LK) reflected by the multifaceted long mirrors (J5, J6) are the corresponding photoconductor drums.
Images on (9Y, 9M, 9C, 9K) and four laser beams (LY, LM,
Exposure scanning for four photoconductor drums (9Y, 9M, 9C, 9K) is simultaneously performed by LC, LK).

In the fifth and sixth embodiments (FIGS. 5 and 6), the laser beams (LY, LM, LC, LK) are reflected only on the reflecting surfaces of the multifaceted long mirrors (J5, J6). Because it is configured,
Significant cost reduction is possible. In addition, the emission directions of the laser beams (LY, LM, LC, LK) to the photoconductor drums (9Y, 9M, 9C, 9K) are non-parallel, and as a result, the photoconductor drums (9Y, 9K)
(M, 9C, 9K) are arranged in an arc shape. For this reason, it is necessary to change the developing device and the paper transport structure, but the size of the housing (H5, H6) is the same as that of the reference example (Fig. 7).
Since the size is significantly smaller than the size of (H), it is possible to effectively downsize the color image forming apparatus.

As in the first to sixth embodiments (FIGS. 1 to 6), the multifaceted elongated mirror (J1, ...) Having a plurality of reflecting surfaces adjacent to each other at different angles is used. With a configuration in which a plurality of beams or a group of beams are reflected by the plurality of reflecting surfaces in different directions, it is not necessary to dispose separate long mirrors corresponding to the respective colors of YMCK for optical path separation. Therefore, the arrangement space is reduced, and the multi-beam scanning optical system can be made compact while having a simple structure. Also, each laser beam (LY, LM, LC, LK)
Since the optical path separating position of can be brought closer to the polygon mirror (1), the loss of the separating space can be eliminated, and the multi-beam scanning optical system can be made more compact.
Since complicated initial adjustment of each beam scanning position (for example, adjustment of relative position / relative angle of each laser beam) is not necessary, adjustment time can be shortened and cost can be reduced. And because it is not necessary to secure a space for adjustment individually,
It is possible to downsize the entire scanning device. Further, the cost can be further reduced by using the multifaceted long mirrors (J1, ...) Produced by resin molding.

Further, since the relative beam interval and the beam angle can be realized with high accuracy by using the multi-faceted elongated mirrors (J1, ...), the image by each laser beam (LY, LM, LC, LK) can be obtained. The positional accuracy between exposures on the surface can be improved. For example, even if the position or angle of each laser beam (LY, LM, LC, LK) deviates slightly in the sub-scanning direction due to environmental changes (temperature / humidity changes, etc.) and changes over time, all laser beams (L
Since Y, LM, LC, and LK are shifted in the same direction, fluctuations in relative position and relative angle between laser beams (LY, LM, LC, and LK) are suppressed. Therefore, the image position shift between each color image
(That is, color shift) can be prevented. The positions and angles of a plurality of beams or beam groups can be adjusted integrally by adjusting the positions and angles of the multifaceted long mirrors (J1, ...), and therefore the number of adjustment steps can be significantly reduced. .

8A, 8B, and 8C, three types of light source units (30A, 30B) used in combination with the multi-beam scanning optical system of each embodiment (FIGS. 1 to 6) are used. , 30C) is shown in the sub-scan section. In FIG. 8, 30A, 30B and 30C are light source parts, 31 is an LD (La
ser diode) chip, 32A, 32B, 32C are optical waveguide substrates, W1, W
2, W3, W4, W1a, W1b, W2a, W2b are optical waveguides, L1, L2, L3, L4, L1
a, L1b, L2a and L2b are laser beams, and M1 and M2 are laser beam groups. The light source unit (30A, 30B, 30C) includes a plurality of LD chips (31) arranged at equal intervals along the sub-scanning direction and one LD chip (31) integrally fixed and held. The optical waveguide substrate (32A, 32B, 32C). Figure 8
Since two LD chips (31) are used in the light source section (30A) shown in (a), two optical waveguides (W1, W2) are also formed in the optical waveguide substrate (32A). There is. 8 (b) and (c)
Since the four LD chips (31) are used in the light source section (30B, 30C) shown in (4), the four optical waveguides (W1a, W1b, W2a, W2b) are also included in the optical waveguide substrate (32B, 32C). ; W1, W2, W3, W4) are formed.

Each optical waveguide (W1, W2, W3, W4, W1a, W1b, W2a, W2b) corresponding to the core in the optical waveguide substrate (32A, 32B, 32C)
Are formed on the silicon substrate with the clad adjacent to the periphery. The entrance end and the exit end are arranged at equal intervals along the sub-scanning direction corresponding to each LD chip (31), and the exit side is narrower than the entrance side. Therefore, a plurality of laser beams (L1, L2, L3, L4, L1a, L) emitted from the LD chip (31) in parallel with each other are used.
1b, L2a, L2b) is an optical waveguide (W1, W2, W3, W4, W1a, W1b, W2a, W2
By entering and propagating in b), the beam interval is narrowed along the sub-scanning direction. Laser beam group (M
In the optical waveguide substrate (32B) that emits (1, M2), a pair of laser beams (L1a, L1b; L2 that compose each laser beam group (M1, M2)
a, L2b) become parallel to each other until the beam reaches the exit end face while narrowing the beam interval. And the optical waveguide (W1, W2, W3,
Each laser beam (L1, L2, L3, L4, L1a, L1b, L2a, L2b) that has reached the emission end of W4, W1a, W1b, W2a, W2b) is emitted as a divergent beam.

Laser beam from the light source section (30A, 30B, 30C)
(L1, L2, L3, L4) or laser beam groups (M1, M2) are emitted in a plurality of monolithically configured optical waveguides (W1, W2, W4).
3, W4, W1a, W1b, W2a, W2b). According to the setting, the light source unit (30A) of FIG. 8 (a) emits two laser beams (L1, L2) that are not parallel to each other, and the light source unit (30C) of FIG. Four non-parallel laser beams (L1, L2, L3, L4) are emitted. Further, the light source unit (30B) of FIG. 8B has two laser beams (L1a, L1b;
Two laser beam groups (M1, M2) composed of L2a, L2b) are emitted non-parallel to each other. Each laser beam (L1, L2, L3, L4, L1a, L1b, L2a, L2b) emitted from the light source unit (30A, 30B, 30C) is converted into substantially parallel light by a condenser lens (not shown), and the cylinder It is converged by a lens (not shown). However, the light source (30A, 3
A plurality of laser beams (L1, L2, L3, L4) or laser beam groups (M1, M2) emitted from (0B, 30C) non-parallel to each other cross each other before entering the condenser lens.

Each laser beam (L1, L2, L3, L4, L1a, L1b, L2a, L2b) emitted from the light source section (30A, 30B, 30C) is near the deflection reflection surface (1S) of the polygon mirror (1). Focuses in the sub-scanning direction to form an image, and multiple laser beams (L1, L2, L3, L
4) Or the laser beam groups (M1, M2) are focused at different angles. The converging direction is the spreading direction of the plurality of laser beams (L1, L2, L3, L4) or the laser beam group (M1, M2) emitted from the light source unit (30A, 30B, 30C) (that is, the sub-scanning direction). Is. Each laser beam (L1, L
2, L3, L4) or laser beam groups (M1, M2) are incident on the same deflective reflection surface (1S) of the polygon mirror (1) at different angles in the sub-scanning direction, and at a predetermined distance from each other. Then, it is deflected and reflected. As a result, the deflection scanning in the main scanning direction and the optical path separation in the sub scanning direction are performed.

By using the light source section (30C) of FIG. 8C, one set can be applied to a multi-beam scanning optical system corresponding to each color of YMCK. On the other hand, the light source unit shown in FIGS.
By using (30A, 30B), two sets can be applied to a multi-beam scanning optical system corresponding to each color of YMCK. Further, in the light source section (30B) of the type that emits the laser beam group (M1, M2), a plurality of beam exposure scans can be performed for one photosensitive drum (9Y, 9M, 9C, 9K). Therefore, it is possible to further increase the speed of color image formation.

[0034]

As described above, the multi-beam scanning optical system according to the present invention has a compact and simple structure, but does not require complicated initial adjustment of each beam position, and further, environmental fluctuations and aging. The change in the beam position due to the change can also be suppressed. Therefore, it is possible to achieve high positional accuracy between exposures and suppress image positional deviation (that is, color deviation) between color images.

[Brief description of drawings]

FIG. 1 is a sub-scanning sectional view showing a first embodiment of a multi-beam scanning optical system.

FIG. 2 is a sub-scanning sectional view showing a second embodiment of a multi-beam scanning optical system.

FIG. 3 is a sub-scanning sectional view showing a third embodiment of a multi-beam scanning optical system.

FIG. 4 is a sub-scanning sectional view showing a fourth embodiment of a multi-beam scanning optical system.

FIG. 5 is a sub-scanning sectional view showing a fifth embodiment of a multi-beam scanning optical system.

FIG. 6 is a sub-scanning sectional view showing a sixth embodiment of a multi-beam scanning optical system.

FIG. 7 is a sub-scanning sectional view showing a reference example of a multi-beam scanning optical system.

FIG. 8 is a sub-scanning cross-sectional view showing a specific example of a light source unit applicable to each embodiment.

[Explanation of symbols]

1… Polygon mirror 1S… Deflection / reflection surface 3,4… fθ lens 5Y, 5M, 5C, 5K, 6M, 6C, 6K… Reflecting mirror 7Y, 7M, 7C, 7K… Long lenses 9Y, 9M, 9C, 9K ... Photosensitive drum J1, J2, J3, J4, J5, J6 ... Multi-faceted long mirror LY, LM, LC, LK ... Laser beam L1, L2, L3, L4, L1a, L1b, L2a, L2b… Laser beam M1, M2 ... laser beam group

Continued front page    F-term (reference) 2C362 AA07 BA04 BA50 BA54 BA87                       DA07                 2H045 BA23 BA34 DA01 DA04                 5C051 AA02 CA07 DA02 DB02 DB22                       DB24 DB30 DC04 DC07 EA01                       FA01                 5C072 AA03 BA01 BA02 BA19 HA02                       HA06 HA09 HA13 HA20 QA14                       XA01 XA05

Claims (5)

[Claims] 1. A multi-beam scanning optical system that guides a plurality of deflected beams or beam groups separately to a plurality of photoconductors and performs image scanning on each of the photoconductors. A multi-beam scanning optical system comprising a multi-faceted long mirror that reflects beams in different directions. 2. The multi-beam scanning optical system according to claim 1, wherein the positions and angles of a plurality of beams or beam groups are integrally adjusted by adjusting the positions and angles of the multifaceted elongated mirrors. system. 3. The multi-beam scanning optical system according to claim 1, wherein a plurality of beams or a group of beams are reflected only on a reflecting surface of the multi-faceted elongated mirror. 4. The multi-beam scanning optical system according to claim 1, wherein the multifaceted long mirror is made of resin. 5. The multi-beam scanning optical system according to claim 1, wherein the beam group is composed of a plurality of beams parallel to each other.