JP3470555B2 - Optical scanning device and image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device and an image forming apparatus such as a laser printer in which the optical scanning device is used. More specifically, the present invention relates to a rotary polygon mirror for a light beam emitted from a light source. The present invention relates to an optical scanning device that is incident on a rotary polygon mirror in a state of being inclined in a sub-scanning direction with respect to a surface perpendicular to a rotation axis, and an image forming apparatus using the optical scanning device.

[0002]

2. Description of the Related Art The applicant of the present application has proposed an optical scanning device 300 shown in FIGS. 14 and 15 as an optical scanning device used in an image recording apparatus such as a laser printer or a digital copying machine (Japanese Patent Application No. Hei 10-135242). 9-42742).

In this optical scanning device 300, a laser beam LB emitted from a laser light source 302 is collimated by a collimator lens 304 and then reflected by a third mirror 306, a fourth mirror 308 and a first mirror 310 in order. Then, the light passes through the fθ lens 316 and enters the mirror surface 314 of the rotary polygon mirror 312. At this time, the mirror surface 314
The incident beam on is inclined in the sub-scanning direction at a predetermined incident angle θ1 from the plane P4 perpendicular to the rotation axis of the rotary polygon mirror 312. The reflected beam that has been changed and scanned in the main scanning direction by the movement of the mirror surface 314 due to the rotation of the rotary polygon mirror 312 is transmitted through the fθ lens 316, reflected again by the first mirror 310, and further reflected by the reflection mirror 318 and the cylindrical mirror 320.
And is incident on the photosensitive drum 322.

As described above, the incident beam on the mirror surface 314 of the rotary polygon mirror 312 and the mirror surface 3 are formed by one first mirror 310.
Since both of the reflected beams from 14 are reflected, the incident angle θ1 of this incident beam is set to a predetermined small angle to prevent the deterioration of the image quality due to the curvature of the scanning line, and the first mirror 3
Since 10 can be installed near the rotary polygon mirror 312,
The width W1 of the optical scanning device 300 can be reduced.

Further, the cylindrical mirror 320 has power in the sub-scanning direction, and corrects variations in scanning lines due to surface tilt of the mirror surface 314 of the rotary polygon mirror 312 (so-called surface tilt correction). As a result, good image quality can be obtained.

However, in this optical scanning device 300, 1
With the first mirror 310, the mirror surface 31 of the rotary polygon mirror 312
Since both the incident beam on the beam No. 4 and the reflected beam from the mirror surface 314 are reflected, if there is an error in the mounting position of the first mirror 310, even if this error is small, the effect of the error is 2 Double. As a result, the deviation of the incident position of the laser beam LB on the cylindrical mirror 320 becomes large, so that the laser beam LB enters the outside of the range in which the surface tilt can be corrected by the cylindrical mirror 320.
It becomes impossible to sufficiently perform the face tilt correction. As a result, variations (pitch unevenness) occur in the scanning line spacing in the sub-scanning direction, which may lead to deterioration in image quality.

[0007]

SUMMARY OF THE INVENTION In consideration of the above facts, an object of the present invention is to obtain an optical scanning device and an image forming apparatus which prevent the scanning lines from curving and have no uneven pitch in the sub-scanning direction.

[0008]

According to a first aspect of the present invention, there is provided a light source for emitting a light beam and a rotary polygonal mirror for reflecting the incident light beam and scanning the light beam in a main scanning direction by rotation. And a light beam incident on the rotary polygon mirror from a direction inclined in the sub-scanning direction with respect to a plane perpendicular to the rotation axis of the rotary polygon mirror, and a reflection for reflecting the light beam reflected by the rotary polygon mirror again. A member, a correction optical component that corrects the optical axis tilt of the light beam in the sub-scanning direction due to the surface tilt of the rotating polygon mirror, and a light beam to the correction optical component that is arranged in the optical path from the light source to the correction optical component. And an adjusting optical component capable of adjusting the incident position of the beam in the sub-scanning direction.

The light beam emitted from the light source is reflected by the reflecting member and is incident on the rotary polygon mirror (hereinafter, the light beam incident on the rotary polygon mirror is referred to as "incident beam"), and is scanned in the main scanning direction. (Hereinafter, the light beam reflected by the rotating polygon mirror is referred to as a "reflected beam"), and is reflected again by the reflecting member. Since the light beam is reflected twice by one reflecting member,
The reflecting member can be brought close to the rotary polygon mirror without interfering with the optical axis of the optical path, and the optical scanning device becomes compact. Further, since the incident angle of the incident beam and the reflection angle of the reflected beam may be small, it is possible to reduce the curvature of the scanning line.

Even if an optical axis tilt of the light beam in the sub-scanning direction occurs due to the surface tilt of the rotary polygon mirror, the correction optical component prevents the tilt of the optical axis, so that a good image can be obtained. Further, even if the incident position of the light beam on the correction optical component is deviated due to the mounting error of the reflecting member, etc., the deviation is eliminated by adjusting the incident position of the light beam in the sub-scanning direction by the adjustment optical component. it can. Therefore, a good image can be obtained without causing pitch unevenness in the sub-scanning direction.

According to a second aspect of the invention, in the first aspect of the invention, the correction optical component is capable of adjusting the irradiation position in the sub-scanning direction.

By adjusting the position of the light beam emitted by the correction optical component in the sub-scanning direction, a good quality image can be obtained. In particular, for example, when a plurality of optical scanning devices are arranged and the light beams from the plurality of optical scanning devices are applied to one photoconductor, the position of the light beam is adjusted in the sub-scanning direction for each optical scanning device, The deviation of the light beam from each optical scanning device can be eliminated.

According to a third aspect of the invention, there is provided the invention according to the first or second aspect, wherein a plurality of the adjusting optical components are provided.

Therefore, since the incident position and the incident angle of the light beam on the tilt correction optical component can be adjusted, tilt correction can be surely performed, and pitch unevenness in the sub-scanning direction does not occur.
It is possible to obtain good image quality.

According to a fourth aspect of the invention, in the invention according to any one of the first to third aspects, the adjusting optical component includes a reflecting member that reflects an incident light beam, and the reflecting member. A rotation adjusting mechanism that adjusts the incident position of the light beam on the correction optical component in the sub-scanning direction by rotating about a rotation axis along the main scanning direction.

By rotating the reflecting member about the rotation axis along the main scanning direction by the rotation adjusting mechanism,
The reflection angle and the reflection direction of the light beam reflected by the reflection member can be adjusted. This makes it possible to easily correct the optical axis tilt of the light beam in the sub-scanning direction without changing the optical path length.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the reflecting member is composed of a folding mirror that folds back the incident light beam, and the rotation adjusting mechanism folds the folding mirror. It is characterized in that it is supported at four points on the surface or the opposite surface.

When the folding mirror is rotated about the rotation axis along the main scanning direction, the change in the reflection angle of the light beam reflected by the folding mirror with respect to this rotation angle is 2 degrees.
Double. That is, it is possible to greatly change the reflection direction of the light beam by simply rotating the folding mirror, and it is possible to easily correct the optical axis tilt in the sub-scanning direction of the light beam.

Further, since the folding mirror is supported at four positions by the rotation adjusting mechanism, it is stable, and the mounting position does not deviate due to vibration or the like.

According to a sixth aspect of the invention, there is provided the above-mentioned first aspect.
To at least one optical scanning device according to claim 5, and at least one photoconductor on the surface of which an image is formed by a light beam scanned in the main scanning direction by the optical scanning device. Is characterized by.

The optical scanning device constituting the image forming apparatus is
Since a good image can be obtained without causing pitch unevenness in the sub-scanning direction, a good image can be obtained on the photoconductor even in the image forming apparatus without causing pitch unevenness in the sub-scanning direction.

[0022]

1 and 2 show an optical scanning device 10 according to an embodiment of the present invention and a photosensitive drum 12 on which a laser beam LB deflected and scanned by the optical scanning device 10 is incident. It is shown.

As shown in FIG. 1, the optical scanning device 10 has a laser beam L whose intensity is modulated according to image information.
It has a laser light source 14 for emitting B in the same direction as the axial direction of the photosensitive drum 12. The laser beam LB emitted from the laser light source 14 is collimated by the collimator lens 16 arranged on the front side in the emission direction of the laser beam LB.

Laser light source 14 and collimator lens 16
Is fixed to the mounting plate portion 20 of the housing 18 shown in FIG. 2, but in FIG. 2, the laser light source 14 and the collimator lens 16 are fixed to the front side of the collimator lens 16 in the emitting direction of the laser beam LB. 3 Hidden in the mirror 22. The laser beam LB made into parallel light by the collimator lens 16 is reflected at a right angle by the third mirror 22.

A fourth mirror 24 is attached to the housing 18 by a rotation adjusting mechanism 170 (see FIGS. 5 to 7) described later. The fourth mirror 24 is the third mirror 2.
The laser beam LB reflected by 2 is reflected upward.

The incident position of the laser beam LB on the reflecting surface 24A of the fourth mirror 24 is set to the reflecting point 24B at the center of the reflecting surface 24A in the height direction. The rotation adjusting mechanism 170 supports the fourth mirror 24 rotatably in the clockwise direction and the counterclockwise direction (arrow B direction) in FIG. 2 about the reflection point 24B. The reflection direction of the laser beam LB by the fourth mirror 24 is slightly tilted from the vertical direction to the third mirror 22 side (right side in FIG. 2).
This tilt angle can be adjusted by rotating the fourth mirror 24.

Further, from the laser light source 14 to the third mirror 22.
The optical axis of the optical path of the laser beam LB through the fourth mirror 24 constitutes one plane P1 as shown in FIG.

A first mirror 26 is fixed to the housing 18 above the fourth mirror 24. Fourth mirror 24
The laser beam LB reflected upwards at 1 is reflected by the first mirror 26 in a substantially horizontal direction (rightward in FIG. 2).

Further, the laser beam LB passes through an fθ lens 29 composed of lenses 28 and 30 fixed to the housing 18, and is incident on a mirror surface 34 of a rotary polygon mirror 32 also attached to the housing 18. The optical axis of the optical path of the laser beam LB from the third mirror 22 to the mirror surface 34 of the rotary polygon mirror 32 through the fourth mirror 24 and the first mirror 26 constitutes one plane P2 as shown in FIG. There is. The plane P2 is orthogonal to the plane P1. Therefore, the twist of the laser beam LB reflected by the third mirror 22, the fourth mirror 24, and the first mirror 26 is reduced, and the image quality is improved.

The rotary polygon mirror 32 has a regular polygonal columnar shape, and a plurality of mirror surfaces 34 are formed on its side surfaces. Rotating polygon mirror 32
Is rotated at a predetermined angular velocity by a motor 36 about a rotation axis J extending along the vertical direction. Due to the rotation of the rotary polygon mirror 32, the laser beam LB incident on the mirror surface 34 of the rotary polygon mirror 32 is reflected by the mirror surface 34 and deflected and scanned at a constant angular velocity. Hereinafter, the deflection scanning direction of the laser beam LB by the rotary polygon mirror 32 is the main scanning direction, and the plane orthogonal to the main scanning direction and including the rotation axis J is the sub-scanning plane (the plane P2 is located in the sub-scanning plane). The direction perpendicular to the main scanning direction is the sub scanning direction.

Here, as shown in FIG. 3, the laser beam LB has a width LW of the laser beam LB in the main scanning direction wider than the surface width 34W of one mirror surface 34 of the rotary polygon mirror 32 by the collimator lens 16. Has a width (so-called overfield optical system), and has a mirror surface 34 in the sub-scanning direction.
Focus on above. In this way, the laser beam L
By making the width LW of B wider than the surface width 34W of the mirror surface 34 of the rotary polygon mirror 32, the number of mirror surfaces 34 is increased by the small rotary polygon mirror 32, and the rotary polygon mirror 32 is rotated at high speed.
Images with high image quality and high resolution can be obtained. Further, since so-called side incidence can be obtained by the rotary polygon mirror 32 having a small beam diameter equivalent to that of the side incidence, power consumption of the motor for rotating the rotary polygon mirror 32 can be reduced and reliability can be improved.

A laser beam LB which is incident on the mirror surface 34 of the rotary polygon mirror 32 from the first mirror 26 (hereinafter, this laser beam LB is referred to as “incident beam”) is a plane orthogonal to the rotation axis J of the rotary polygon mirror 32. The light is incident on the mirror surface 34 of the rotary polygon mirror 32 at a predetermined incident angle θ with an inclination from P3 in the sub-scanning direction. Therefore, the laser beam LB reflected by the mirror surface 34 of the rotary polygon mirror 32 (hereinafter, this laser beam LB is also referred to as “reflected beam”) is sub-scanned from the surface P3 at a predetermined reflection angle θ equal to the incident angle θ. Since the light beam is inclined in the direction and reflected, the optical path of the incident beam does not overlap with the optical path of the reflected beam. Further, the incident angle θ is set to be small in order to prevent the vertical movement of the reflection point on the mirror surface 34 due to the rotation of the rotary polygon mirror 32 and to prevent the scanning line from being curved.

Further, as shown in FIG. 3, the positions of the first mirror 26 and the rotary polygon mirror 32 are determined so that the incident beam is incident on the rotation axis J of the rotary polygon mirror 32, that is, so-called front incidence. Has been.

As shown in FIGS. 1 and 2, the reflected beam reflected by the mirror surface 34 at a predetermined reflection angle θ is again f
It is a so-called double-pass optical system that passes through the θ lens 29. Further, the fθ lens 29 has power only in the main scanning direction, keeps the moving speed in the main scanning direction constant when the laser beam LB is incident on the photoconductor drum 12, and performs main scanning with the laser beam LB. The image is focused on the photoconductor drum 12 by focusing in the direction. After being collimated by the collimator lens 16, the laser beam LB is narrowed in the sub-scanning direction by a cylinder lens or a spherical lens (not shown), reflected by the mirror surface 34, and further narrowed by the cylindrical mirror 40. An image is formed on the photosensitive drum 12.

The laser beam LB that has passed through the fθ lens 29 is incident on the first mirror 26 again. First mirror 2
At 6, the laser beam LB is reflected downwards.

Here, as shown in FIG. 2, the optical path R1 of the incident beam and the optical path R2 of the reflected beam are defined by the rotating polygon mirror 3
Gradually move away as you move away from 2. For this reason,
Laser beam L reflected substantially downward by the first mirror 26
The optical path R4 of B is further away from the optical path R3 of the laser beam LB from the fourth mirror 24 to the first mirror 26.
As a result, the laser beam LB reflected substantially downward by the first mirror 26 does not enter the third mirror 22 and is transmitted through the transmission hole 20A (see FIG. 2) formed in the housing 18 to allow the laser beam to pass through the housing 18. External reflection mirror 3
It is incident on 8.

The reflection mirror 38 is attached to the housing (not shown) of the image forming apparatus by a rotation adjusting mechanism 110 similar to the rotation adjusting mechanism 170 that rotatably supports the fourth mirror 24.

The incident position of the laser beam LB on the reflecting surface 38A of the reflecting mirror 38 is set at a reflecting point 38B at the center of the reflecting surface 38A in the height direction. The reflection point 38B is
It is positioned linearly along the main scanning direction on the reflecting surface 38A. Then, the rotation adjusting mechanism 110 uses the reflection point 3
The reflecting mirror 38 is supported rotatably in the clockwise direction and the counterclockwise direction (arrow D direction) in FIG. Since the reflection direction of the laser beam LB by the reflection mirror 38 can be rotated at the reflection point 38B, it can be adjusted by rotating the reflection mirror 38 without changing the optical path length.

The laser beam LB reflected obliquely upward by the reflecting mirror 38 enters the cylindrical mirror 40. The cylindrical mirror 40 has power only in the sub-scanning direction, and corrects variations in scanning lines due to surface tilt of the mirror surface 34 of the rotary polygon mirror 32 (so-called surface tilt correction).

The laser beam LB reflected substantially downward by the cylindrical mirror 40 is the photosensitive drum 12
Incident on. The rotation of the rotary polygon mirror 32 causes the laser beam LB to move in the main scanning direction on the surface of the photosensitive drum 12. Further, the photosensitive drum 12 is rotated by a driving unit such as a motor (not shown), and the laser beam LB moves on the surface of the photosensitive drum 12 in the sub scanning direction. As a result, a latent image is formed on the surface of the photoconductor drum 12.

Now, the rotation adjusting mechanism 110 for rotatably supporting the reflection mirror 38 will be described.

As shown in FIGS. 5 to 7 and 9, the rotation adjusting mechanism 110 has a pair of plate-shaped plates 112 and 114 arranged on both sides of the reflecting mirror 38 in the longitudinal direction. (In FIG. 9, only the plate 114 is shown for convenience of illustration, but the plate 112 also has substantially the same configuration as the plate 114.) Plates 112, 114
Insertion holes 116 into which both longitudinal ends of the reflection mirror 38 are respectively inserted are formed in the.

As shown in FIG. 9, the insertion hole 116 is formed in a substantially rectangular shape which is slightly larger than the side surface 38C of the reflection mirror 38. In the insertion hole 116, the reflection mirror 38
On the reflective surface 38A side, a support portion 118 whose upper and lower portions bulge toward the inside of the insertion hole 116 is formed.
Further, the lower surface 38D of the reflection mirror 38 is inserted into the insertion hole 116.
Side, the supporting portion 1 bulging toward the inside of the insertion hole 116.
20 are formed.

On the side of the rear surface 38E of the reflecting mirror 38 opposite to the reflecting surface 38A, the insertion hole 116 is expanded in a rectangular shape to form a spring accommodating portion 122, and the end surface inserted into the spring accommodating portion 122 is formed. The reflection mirror 38 is sandwiched between the support portion 118 and the substantially U-shaped spring 124, and is positioned in the thickness direction. Similarly, the support portion 12 is formed by the end surface substantially U-shaped spring 126 inserted between the upper surface 38F of the reflection mirror 38 and the insertion hole 116.
The reflection mirror 38 is sandwiched between the position 0 and 0, and is positioned in the height direction. The ends of the springs 124, 126 are bent outward to form positioning plate parts 124A, 126A. The positioning plate parts 124A, 126A hit the reflection mirror 38 or the plates 112, 114 to cause the spring 12 to move.
4, 126 are positioned. Also, the springs 124, 12
6, the holes 124B and 126B are formed in the spring housing portion 1
22 and a projection (not shown) projecting from the end surface of the insertion hole 116 are engaged with each other to prevent the springs 124 and 126 from coming off.

A pair of substantially crescent-shaped bosses 128 are provided on the outer surfaces of the plates 112 and 114 on the opposite side to the facing surfaces. The arc surface 128A of the boss 128 is formed in an arc shape centered on the incident point 38B of the reflection mirror 38 attached to the plates 112 and 114.

Brackets 132 and 134 are arranged in surface contact with the outer surfaces of the plates 112 and 114.
The bracket 132 is formed in a substantially T shape in a plan view, and the bracket 134 is formed in a substantially L shape in a plan view, and positioning pins 140 projecting from the respective short piece portions 136, 138.
Is inserted and positioned in a positioning recess of a casing (not shown), and is further fixed to the casing by inserting a screw (not shown) into the screw hole 115 (the screw hole 115 of the racket 132 is not shown). . In this state, the bracket 13
2 of the long piece 142 and the long piece 144 of the bracket 134
And face each other in parallel.

As shown in FIG. 8, the bracket 132,
The long piece portions 142 and 144 of the 134 are provided with long holes 1 each having a substantially oval shape.
46 is formed. (In FIG. 8, only the bracket 134 is shown for convenience of illustration, but the bracket 132 also has substantially the same configuration as the bracket 134 except for the shape of a short piece portion 138 described later.) The arc portion of the elongated hole 146. 146A is formed with the same radius corresponding to the arc surface 128A of the boss 128, and the boss 128 has a long hole 146.
The arc surface 128A of the boss 128 is
It is in surface contact with the circular arc portion 146A of the long hole 146. In this state, the screw 148 is inserted into the insertion holes 147 formed in the brackets 132 and 134, and the plates 112 and 11 are inserted.
4 are temporarily fixed to the brackets 132 and 134, respectively. The inner diameter of the insertion hole 147 is formed to be larger than the outer diameter of the male screw of the screw 148, so that the plates 112 and 114 can rotate with respect to the brackets 132 and 134 in the temporarily fixed state, as will be described later. ing.

The circular arc portion 146A of the long hole 146 is formed on the boss 12
It is formed longer than the circular arc surface 128A. Therefore, the plates 112 and 114 are attached to the brackets 132 and 13.
4, the plates 112 and 114 rotate about the incident point 38B of the reflection mirror 38 with respect to the brackets 132 and 134. At this time, arc surface 1
28A comes into surface contact with the arc portion 146A, and the plate 11
Guide the rotation of 2,114.

From the brackets 132 and 134, an adjusting projection 150 is provided so as to project downward. An adjustment block 154 is attached to the adjustment protrusion 150 with an adjustment screw 152. By rotating the adjusting screw 152, the adjusting block 154 is moved to the long piece portions 142, 1
It can be moved in the extending direction of 44 (left and right direction in FIG. 7).

An adjusting pin 156 is projected from the adjusting block 154, and the adjusting pin 156 is inserted into a long hole 160 of an adjusting protrusion 158 protruding downward from the plates 112 and 114. ing. Therefore, when the adjusting block 154 is moved by rotating the adjusting screw 152, the adjusting pin 156 pushes the inner wall of the long hole 146,
The plates 112, 114 move relative to the brackets 132, 134. This allows the plates 112, 114 to
Rotates with respect to brackets 132,134. By this rotation, after setting the reflection mirror 38 at a desired angle,
Tighten the screws 148 with a predetermined torque to secure the plates 112, 1
14 is fixed to the brackets 132 and 134.

The rotation adjusting mechanism 17 for the fourth mirror 24
0 has the same structure as the rotation adjusting mechanism 110 of the reflection mirror 38, but in the rotation adjusting mechanism 170, the short piece portions 136 and 138 of the brackets 132 and 134 are included.
Is attached to the housing 224 of the optical scanning device 10, and this point is different from the rotation adjusting mechanism 110.

Next, the optical scanning device 1 according to the embodiment
The action of 0 will be described. As shown in FIG. 1, the laser light source 1
The laser beam LB emitted from the collimator lens 4 is collimated by the collimator lens 16 and then collimated.
The light is reflected by the second, fourth, and fourth mirrors 24, 26 in order, and enters the mirror surface 34 of the rotary polygon mirror 32. The laser beam LB deflected and scanned in the main scanning direction by the movement of the mirror surface 34 due to the rotation of the rotary polygon mirror 32 passes through the fθ lens 29, is reflected by the first mirror 26 again, and is further reflected by the reflection mirror 38 and the cylindrical mirror 40. It is reflected and enters the photoconductor drum 12.

As described above, the laser beam LB emitted from the laser light source 14 is reflected by the third mirror 22 at a right angle and then is incident on the fourth mirror 24. For this reason,
For example, when the laser beam LB emitted from the laser light source 14 is made to go straight and be incident on the fourth mirror 24, the cylindrical mirror 40 is provided below the fθ lens 29 or the rotary polygon mirror 32 so that the optical path of the laser beam LB is below. The cylindrical mirror 40 and the laser light source 14 must be arranged so as not to interfere with each other, and layout restrictions are imposed. However, the optical scanning device 10 according to the first embodiment has such layout restrictions. Without receiving
The degree of freedom in layout is high.

Further, since the laser beam LB is reflected by the first mirror 26 to be incident on the mirror surface 34 of the rotary polygon mirror 32, and the reflected beam from the mirror surface 34 is reflected again by the first mirror, the incident beam Incident angle θ
Is maintained at a predetermined small angle, and the first mirror 26 can be installed at a position close to the rotary polygon mirror 32 without interfering with the optical path of the incident beam or the reflected beam of the first mirror 26. Thereby, the deterioration of the image quality due to the curvature of the scanning line is reduced, and the first mirror 26 does not interfere with the optical path of the incident beam or the optical path of the reflected beam, and the width W of the optical scanning device 10 is compared with the conventional one. Can be made smaller.

Further, since the incident beam is incident on the mirror surface 34 of the rotary polygon mirror 32 from the front, even if the scanning line is slightly curved, the curvature becomes bilaterally symmetric with respect to the sub-scanning surface and the deterioration of the image quality is prevented. You can Furthermore, since the laser beam LB projected on the mirror surface 34 of the rotary polygon mirror 32 is minimized by such front incidence, the surface width 34W of the mirror surface 34 of the rotary polygon mirror 32 can be reduced. it can. As a result, the number of mirror surfaces 34 can be increased, or the size of the rotary polygon mirror 32 can be reduced to reduce the load on the motor 36, thereby reducing power consumption and improving reliability.

Lenses 28 and 3 constituting the fθ lens 29
0 is arranged between the rotary polygon mirror 32 and the first mirror 26, and between the rotary polygon mirror 32 and the first mirror 26 is 0.
For example, the distance between the incident beam and the reflected beam is narrower than that between the first mirror 26 and the third mirror 22. Therefore, even if the height of the lenses 28 and 30 is lowered, both the incident beam and the reflected beam pass through the lenses 28 and 30. The lens 2 is provided between the first mirror 26 and the third mirror 22.
8 and 30 may be arranged.

Since the fourth mirror 24 is rotatably supported by the rotation adjusting mechanism 170, the direction of the reflected laser beam LB can be adjusted by the rotation. By this adjustment, the direction of the laser beam LB reflected from the rotary polygon mirror 32 again by the first mirror 26 and incident on the reflection mirror 38 is finely adjusted, and the incident position on the reflection surface 38A is set to the reflection point 38B. You can

Similarly, since the reflection mirror 38 is rotatably supported by the rotation adjusting mechanism 110, the direction of the reflected laser beam LB can be adjusted by rotation. By this adjustment, the incident position of the laser beam LB incident on the cylindrical mirror 40 can be set to the incident point 40A. As a result, the cylindrical mirror 40 can reliably correct pitch unevenness due to the surface tilt of the rotary polygon mirror 32, and the photosensitive drum 12
A good image is obtained on top.

On the other hand, even when the fourth mirror 24 and the reflection mirror 38 are fixed so as not to rotate, the respective mirrors (first mirror 2) constituting the optical scanning device 10 are fixed.
6) and other optical components (fθ lens 29 etc.) or if the installation error is within the allowable range, the laser beam LB is incident near the incident point 40A of the cylindrical mirror 40. Rotating polygon mirror 3
It is possible to surely correct the pitch unevenness due to the surface tilt of No. 2 (usually, the mounting error of each mirror and other optical parts is within the allowable range). However, if the mounting error exceeds the allowable range, the laser beam The LB is incident on a position far away from the incident point 40A of the cylindrical mirror 40, and the surface tilt correction cannot be sufficiently performed. As a result, the scanning lines on the photoconductor drum 12 have uneven pitches as shown in FIG. 10 (in FIG. 10, the image formed on the photoconductor drum 12 is developed on the surface of the photoconductor drum 12). (The left side of the paper surface is the main scanning direction, and the upper direction of the paper surface is the sub-scanning direction. Each scanning line is indicated by the symbol SL.)

However, in the optical scanning device 10 according to the present embodiment, even if the mounting error of each mirror or other optical component exceeds the allowable range, the fourth mirror 24 is rotated, First, the incident position of the laser beam LB on the reflection mirror 38 can be set as the incident point 38B, and further, by rotating the reflection mirror 38, the incident position of the laser beam LB incident on the cylindrical mirror 40 can be changed to the incident point 40A. Therefore, it is possible to surely correct the pitch unevenness due to the surface tilt of the rotary polygon mirror 32. Particularly, in the optical scanning device 10 according to the present embodiment, the first mirror 26 reflects the laser beam LB twice, so that the mounting error of the first mirror 26 is caused by the laser beam L.
Compared with a mirror that reflects B once, its influence is doubled (that is, the deviation in the reflection direction of the laser beam LB is doubled). However, even in this case, the fourth mirror 24 and the reflection mirror 38 can be rotated to set the incident position of the laser beam LB incident on the cylindrical mirror 40 to the incident point 40A.

The reflecting mirror 38 and the fourth mirror 24 are respectively supported by the supporting portion 118 formed in the insertion hole 116 at two positions on the widthwise end of the reflecting surface 38A. Therefore, as indicated by a point 162 in FIG. 11, the reflecting mirror 38 as a whole is supported at two positions at both ends in the width direction of the reflecting surface 38A, for a total of four positions. Thus, by supporting the reflecting surface 38A at four places, the reflecting mirror 38A
Can be stably supported, and the mounting position is not displaced even by vibration or the like, so that the mounting reliability is improved.
Further, in order to stably support the reflection mirror 38 against vibrations and the like, the rear surface 38E is supported substantially at the center, and the reflection mirror 38 is bent to correct the scanning line. However, even in such a case, since the reflecting surface 38A is supported at four places, the reflecting mirror 38 is stably supported and can be held with high reliability.

On the other hand, as indicated by a point 164 in FIG. 12, the reflecting surface 38A of the reflecting mirror 38 can be supported at three places. That is, the plate 112 or the plate 114
In either one of the
Only one is formed at approximately the center of 6 in the height direction. This allows
One end (the right end in FIG. 12) of the reflecting surface 38A is supported at two places, and the other end (the left end in FIG. 12) is supported at one place. Even when the reflecting mirror 38 is supported at three places as described above, the reflecting mirror 38 can be stably supported. Further, since the flat surface is formed by these three places, higher accuracy is not required for the protruding height of the supporting portion 118 as compared with the case of supporting at four places.

The rotation adjusting mechanisms 170 and 11 described above are used.
By using 0, not only the reflection mirror 38 and the fourth mirror 24 but also, for example, the cylindrical mirror 40 can be rotatably supported. That is, the longitudinal ends of the cylindrical mirror 40 are respectively connected to the plates 112 and 11 respectively.
4 and the brackets 132, 134.
Is fixed to a casing (not shown). As a result, the cylindrical mirror 40 is rotated to rotate the cylindrical mirror 40.
By finely adjusting the reflection direction of the laser beam LB reflected by, the irradiation position of the laser beam LB on the photoconductor drum 12 can be set to the incident point 40A, so that there is no deviation of the scanning line in the sub-scanning direction. .

In FIG. 13, four image forming units 70K including the optical scanning devices 10K, 10Y, 10M and 10C and the photoconductor drums 12K, 12Y, 12M and 12C, which are similar to those of the first embodiment of the present invention, are provided. 70Y, 70M, 7
0C, and these image forming units 70K, 70K
Color laser printer 7 with Y, 70M and 70C arranged
Two main parts are shown. Color laser printer 72
Then, the image forming units 70K, 70Y, 70M, 70
An image of K (black), Y (yellow), M (magenta), and C (cyan) is formed by each of C.

The color laser printer 72 has a transparent endless conveying belt 82 which is wound around four rollers 74, 76, 78 and 80. Conveyor belt 82
Is rotated at a constant speed in the counterclockwise direction in FIG. 7 (direction of arrow A) by a driving means such as a motor (not shown). Roller 74
The conveyor belt 82 between the roller and the roller 76 is flat, and the paper S is conveyed on the flat surface 82A.

Above the flat surface 82A, the image forming units 70K, 70Y, 70M and 70C are mounted on the photosensitive drum 1.
2K, 12Y, 12M, and 12C are installed at predetermined intervals along the direction orthogonal to the axial direction, and
K, 12Y, 12M and 12C are the transport belts 8 respectively.
It is in contact with the second flat surface 82A.

The sheets S discharged from a tray (not shown) and conveyed on the flat surface 82A by the rotation of the conveyor belt 82 are in order on the photosensitive drums 12K, 12Y, 12M, 12.
Below C is the photoconductor drums 12K, 12Y, 12M, 12C.
It is passed while being sandwiched between the outer periphery of and the flat surface 82A. At this time, the respective photosensitive drums 12K, 12Y, 12M,
Toner images of different colors are transferred from 12C. After that, the conveyor belt 82 goes around downward by the rollers 76 and 78, and the paper S is separated from the conveyor belt 82. An image is fixed on the sheet S by a fixing device (not shown), and the sheet S is fixed.
An image of four colors is obtained.

As described above, the four image forming units 70
Even when the color laser printer 72 is configured by arranging K, 70Y, 70M, and 70C, the width W of each image forming unit 70K, 70Y, 70M, and 70C is smaller than that of the conventional one. The width of the printer 72 is smaller than that of the conventional printer.

Further, the optical scanning devices 10K, 10Y, 1
The 0M and 10C reflection mirrors 38 and the fourth mirror 24 are
It can be rotated by the rotation adjusting mechanism, and by doing so, it is possible to eliminate pitch unevenness in the sub-scanning direction in each of the optical scanning devices 10K, 10Y, 10M, and 10C, so that a good image is obtained.

Further, the optical scanning devices 10K, 10Y,
The cylindrical mirrors 40 of 10M and 10C can also be rotated by the rotation adjusting mechanism, and as a result, the paper S is removed by the optical scanning devices 10K, 10Y, 10M, and 10C.
A good image can be obtained because there is no misregistration between colors (so-called color misregistration).

As a method of eliminating the above-mentioned color shift, each optical scanning device 10K, 10K is formed on the transfer belt 82.
A detection pattern that is separate from the image is formed for each of Y, 10M, and 10C, and a color shift is detected by reading the detection pattern with a sensor.
There is also a method of adjusting the position of each mirror that constitutes the optical scanning devices 10K, 10Y, 10M, and 10C. However, in this method, if the detection patterns themselves of the respective colors overlap, the detection accuracy becomes low. Even in this case, in the color laser printer 72 according to the present embodiment, first,
By adjusting the rotation of the cylindrical mirror 40, it is possible to eliminate the overlapping of the detection patterns for each color. As a result, highly accurate detection is possible, and the optical scanning devices 10K, 10Y, and 10 are controlled by feedback control.
The positions of the respective mirrors forming M and 10C can be adjusted accurately, and high image quality can be obtained.

In FIG. 13, four image forming units 70 are provided.
Although the case where the color laser printer 72 is configured by arranging K, 70Y, 70M, and 70C is shown, the number of image forming units forming the image forming apparatus is not limited to this. As the photoconductor, not only the photoconductor drums 12K, 12Y, 12M and 12C described above but also photoconductor belts corresponding to a plurality of image forming units can be used. For example, the image forming apparatus may be configured by one image forming unit, or the image forming apparatus may be configured by five or more image forming units. The photosensitive surface of the photoconductor may be divided in the main scanning direction or the sub-scanning direction, and a plurality of image forming units may be provided to scan each of the divided images. Further, the optical scanning device forming the image forming unit may be the optical scanning device 50 according to the second embodiment or the optical scanning device 60 according to the third embodiment.

It should be noted that the first mirror 26 and the second mirror 62 in each of the above-mentioned embodiments do not necessarily have to be constructed by one mirror. For example, the first mirror 26 may be divided into a mirror in a portion where the laser beam LB from the third mirror is incident and a mirror in a portion where the laser beam from the rotating polygon mirror 32 is incident. Even in this case, if the reflecting surfaces of the respective mirrors satisfy the condition that they are located in the same plane, these two mirrors are brought close to the rotary polygon mirror 32 without interfering with the optical path. Moreover, since the incident angle θ of the incident beam and the reflection angle θ of the reflected beam can be reduced, the width of the image forming apparatus can be reduced without degrading the image quality. The number of parts can be reduced by using one first mirror.

Further, the fθ lens 29 constituted by the lenses 28 and 30 arranged between the rotary polygon mirror 32 and the first mirror 26 is arranged so as to pass both the incident beam and the reflected beam. It may be omitted, and the fθ lens 38 that allows only the reflected beam to pass therethrough may be used. In this case, since it is not necessary to consider the passage of the incident beam, f
As compared with the θ lens 29, the height of the fθ lens 38 can be further reduced. The fθ lens 29 is disposed between the rotary polygon mirror 32 and the first mirror 26.
However, the height of the optical transmission member can be reduced in this case as well.

Further, in the above description, the case of the overfield optical system has been described, but the optical scanning device according to each embodiment can be applied to the case of the underfield optical system.

Further, not only the optical scanning device in which the incident beam and the reflected beam on the rotary polygon mirror 32 are inclined in the sub-scanning direction from the plane P3 orthogonal to the rotation axis J of the rotary polygon mirror 32, but also the rotary polygon mirror. An optical scanning device in which the incident beam and the reflected beam to 32 are not inclined in the sub-scanning direction or an optical scanning device in which the laser beam LB is not reflected twice by one mirror is also applicable. it can.

[0077]

According to the first aspect of the present invention, since there is an adjusting optical component arranged in the optical path from the light source to the tilt correcting optical component and capable of adjusting the incident position of the light beam on the tilt correcting optical component in the sub-scanning direction. A good image can be obtained without causing pitch unevenness in the sub-scanning direction.

According to the second aspect of the present invention, since the correction optical component has the irradiation position adjustable in the sub-scanning direction, the position of the light beam emitted by the correction optical component is adjusted in the sub-scanning direction. With that, a high quality image can be obtained.

According to the third aspect of the present invention, since a plurality of adjusting optical components are provided, the incident position of the light beam on the tilt correction optical component can be adjusted by the plurality of adjusting optical components.
It is possible to adjust the incident position of the light beam on the correction optical component in a wide range.

According to the fourth aspect of the invention, the adjustment optical component rotates about the rotation axis along the main scanning direction to adjust the incident position of the light beam on the tilt correction optical component in the sub scanning direction. Since it has a mechanism, it is possible to easily correct the optical axis tilt of the light beam in the sub-scanning direction without changing the optical path length.

According to the fifth aspect of the invention, the adjusting optical component is a folding mirror that folds back the incident light beam, and the folding mirror has the folding surface or the opposite surface supported at four places. , Stable and supported.

In the invention of claim 6, claims 1 to 5 are provided.
At least one optical scanning device according to any one of
At least one photoconductor on which an image is formed on the surface by the light beam scanned in the main scanning direction by the optical scanning device. Therefore, a good image is formed on the photoconductor without uneven pitch in the sub-scanning direction. Got on.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of an optical scanning device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of an optical scanning device according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a rotary polygon mirror and a laser beam in the optical scanning device according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a plane in which an optical path of a laser beam is formed in the optical scanning device according to the embodiment of the present invention.

FIG. 5 is a perspective view showing a rotation adjusting mechanism of the optical scanning device according to the embodiment of the present invention.

FIG. 6 is a perspective view showing a rotation adjusting mechanism of the optical scanning device according to the embodiment of the present invention.

FIG. 7 is a side view showing a rotation adjusting mechanism of the optical scanning device according to the embodiment of the present invention.

FIG. 8 is a side view showing a plate forming a rotation adjusting mechanism of the optical scanning device according to the embodiment of the present invention.

FIG. 9 is a side view showing a bracket which constitutes a rotation adjusting mechanism of the optical scanning device according to the embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a state where pitch unevenness occurs in an image in a state where the surface of the photosensitive drum is expanded.

FIG. 11 is an explanatory diagram showing a reflection mirror that is supported at four places in the optical scanning device according to the embodiment of the present invention.

FIG. 12 is an explanatory diagram showing a reflection mirror that is supported at three points in the optical scanning device according to the embodiment of the present invention.

FIG. 13 is a schematic cross-sectional view showing an image forming apparatus in which a plurality of optical scanning devices according to an embodiment of the present invention are arranged.

FIG. 14 is a perspective view showing a main part of a conventional optical scanning device.

FIG. 15 is a cross-sectional view showing a main part of a conventional optical scanning device.

[Explanation of symbols]

10 Optical scanning device 10K optical scanning device 10Y Optical scanning device 10M optical scanning device 10C optical scanning device 12 Photosensitive drum 12K photoconductor drum 12Y photoconductor drum 12M photoconductor drum 12C photoconductor drum 14 Laser light source (light source) 22 Third mirror (reflection member) 24 4th mirror (adjustment optical component) 26 1st mirror (reflection member) 32 rotating polygon mirror 38 Reflective mirror (adjustment optical component) 40 Cylindrical mirror (correction optics) 70K image forming unit 70Y image forming unit 70M image forming unit 70C image forming unit 72 Color laser printer (image forming device) 110 rotation adjustment mechanism 170 Rotation adjustment mechanism

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyasu Ishizuka 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Zerox Co., Ltd.Ebina Business Office (72) Inventor Tomohide Ezawa 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Ebina Works (56) References JP 10-239626 (JP, A) JP 7-27991 (JP, A) JP 8-234129 (JP, A) JP 9-127448 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 26/10

Claims (6)

(57) [Claims] 1. A light source that emits a light beam, a rotating polygon mirror that reflects the incident light beam and scans the light beam in the main scanning direction by rotation, and a surface perpendicular to the rotation axis of the rotating polygon mirror. A light beam incident on the rotating polygon mirror from a direction inclined with respect to the sub-scanning direction, and a reflecting member that reflects the light beam reflected by the rotating polygon mirror again; A correction optical component that corrects the optical axis tilt in the sub-scanning direction, and is arranged in the optical path from the light source to the correction optical component,
An optical scanning device comprising: an adjusting optical component capable of adjusting an incident position of a light beam on a correction optical component in a sub-scanning direction. 2. The correction optical component is capable of adjusting an irradiation position in a sub-scanning direction.
The optical scanning device according to. 3. The optical scanning device according to claim 1, wherein a plurality of the adjusting optical components are provided. 4. The adjusting optical component reflects the incident light beam, and a light beam to the correction optical component by rotating the reflecting member around a rotation axis along the main scanning direction. A rotation adjusting mechanism that adjusts the incident position of the light in the sub-scanning direction, and the optical scanning device according to any one of claims 1 to 3. 5. The reflection member is composed of a folding mirror that folds back an incident light beam, and the rotation adjusting mechanism supports the folding mirror at four positions, namely, a folding surface or an opposite surface thereof. The optical scanning device according to claim 4. 6. An image is formed on a surface by at least one optical scanning device according to claim 1 and a light beam scanned in the main scanning direction by the optical scanning device. An image forming apparatus comprising: one photosensitive member;