JPH06202018A - Laser beam scanning device - Google Patents

Abstract

PURPOSE:To prevent a laser beam scanning unit and a mirror unit from vibrating and to form an image of high quality without irregularity of scanning by supporting the optical scanning unit and mirror unit on independent support members which cross each other at right angles. CONSTITUTION:The optical scanning unit 10 which deflects the laser light from a laser light source by a rotary polygon mirror and makes a linear scan at an equal speed through an f-theta lens system is positioned and fixed on an optical stay 1 which is arranged horizontally. A hole 1a which enables the mirror unit 20 being a color slurring correcting device including a couple of roof-shaped mirrors to be arranged, is formed in the optical stay 1. A front plate 2 and a rear plate 3 are abut on both end parts of the optical stay 1 and are fixed with screws 4, and an image station is positioned at the front plate 2 and rear plate 3. The mirror unit 20 is fitted to a stay 5 and this fitting station 5 is fixed to L-shaped fitting bases 5F and 5R, fixed to the front plate 2 and rear plate respectively, with screws from above the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer or a copying machine, and more particularly to an image (latent image) on a plurality of image carriers.
The present invention relates to a laser beam scanning device having a correction mechanism of a color misregistration of a scanning line when forming an image.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus adopting an electrophotographic system, an electrophotographic photosensitive member as an image bearing member is charged by a charger, and the photosensitive member is irradiated with light according to image information so as to be latent. An image is formed by forming an image and transferring the developed image obtained by developing the latent image by a developing device to a sheet material or the like as a recording material.

On the other hand, with the colorization of images, a plurality of image carriers for each of these image forming processes are provided, and each color image of a cyan image, a magenta image, a yellow image, and preferably a black image is carried. There is also proposed an image forming apparatus that forms a full-color image by forming a full-color image on a sheet and superimposing and transferring each color image on a sheet material at a transfer position of each image carrier.

Since such a full-color image forming apparatus has an image forming section for each color, it is advantageous for speeding up. Further, since the sheet material conveying path can be configured in a straight line, it has an advantage that it is adaptable to sheet materials such as thick paper and trapen. On the other hand, there is a problem in how to properly register the images formed by different image forming units. This is because the deviation of the image forming positions of the four colors transferred to the sheet material finally appears as a color deviation or a change in color tone.

In view of the above problems, it has been proposed to control the position of a folding mirror that reflects a laser beam emitted from a laser light source by a stepping motor before the laser beam is emitted to a photosensitive member. . This structure is very effective in preventing color misregistration.

This conventional example will be described below.

In FIG. 4, the image forming apparatus is provided with four image forming stations, and each image forming station has a photosensitive drum 201a, 201b, which serves as an image carrier.
201c and 201d are provided respectively, and there are dedicated charging means (202a, 202b, 202c, 20) around them.
2d), exposure means 203 such as a laser scanner for irradiating the photosensitive drum with light according to image information, developing means (204a, 204b, 204c, 204d), transfer means (205a, 205b, 205c, 205d) ,
Cleaning means (206a, 206b, 206c, 2
06d) are arranged respectively. Here, the image forming stations Pa, Pb, Pc and Pd are for forming a cyan image, a magenta image, a yellow image and a black image, respectively.

On the other hand, each of the image forming stations Pa to Pb
Through the photosensitive drums 201a, 201b,
Endless belt-shaped conveying means 2 below 201c and 201d
07 is arranged, and the paper feeding roller 208 is used to feed the paper feeding table 230.
A sheet material 209 such as paper fed from is guided by a guide 231 and is transported by the transport means 207 through the transfer means 205a to 205d of the image forming stations Pa to Pd. The conveying means 207 is provided with a charger (207b) for charging the electrostatic attraction belt 207a and a static eliminator 207c for neutralizing the belt (207a), and the sheet material 209 is electrostatically attracted to the belt 207a. Adsorb on and transport.

In such a structure, first, the photosensitive drum 201 is formed by the charging means 202a of the first image forming station Pa and known electrophotographic process means such as exposure means.
After forming a latent image of the cyan component color of the image information on a,
The latent image is visualized as a cyan toner image by a developing material having a cyan toner in the developing means 204a and is transferred to the transferring means 2
The cyan toner image is transferred at 05a.

After that, the cyan image and the black image are formed in the same manner, and when the four color toner images are superposed on the sheet material 209, the sheet material 209 is finished.
Is heated and fixed by the fixing unit 210, and a full-color image is obtained on the sheet material 209.

Each of the photosensitive drums 201a to 201d after the transfer is cleaned by the cleaning means 206a to
At 206d, residual toner is removed from each drum and subsequent imaging is provided.

FIG. 5 is a schematic view showing a conventional optical path.

This is because a laser beam emitted from a laser light source (not shown) is bidirectionally scanned by a rotary polygon mirror rotating in the direction of the arrow B in the center of the drawing to produce cyan (C), magenta (M), yellow (Y), After passing through the fθ lens (not shown) corresponding to black (Bk),
After passing through the lens, the mirrors 104C, 104M, 104
Scanning lines 102C, 102M, through Y, 104Bk
Photosensitive drums 201a, 201b, 201c, 20 that rotate in the direction of arrow A in the figure by 102Y, 102Bk
The image information is exposed on 1d, and a multiple image is formed by multiple transfer onto a transfer material 209 conveyed in the arrow X direction in the figure through a known image forming process.

In an apparatus having a plurality of image forming stations as described above, images of different colors are sequentially transferred onto the same surface of the same transfer material. Therefore, when the transfer image position in each image forming station deviates from the ideal position, For example, in the case of a multi-color image, the image intervals of different colors are shifted or overlapped, and in the case of a color image, the difference in tint is caused, and when the degree is more severe, the color shift occurs, which significantly deteriorates the image quality. It was

By the way, as shown in FIGS. 6 (a), (b), (c) and (d) as the types of positional deviation of the transfer image, the positional deviation (top direction) in the scanning line writing direction (top direction in the drawing) is performed. (Margin) ((a) in the figure), positional deviation in the scanning direction (B direction orthogonal to A direction in the figure) (left margin) ((b) in the figure), inclination deviation in the oblique direction ((c) in the figure) , There is a deviation of the magnification error ((d) in the figure), and in reality, the deviations of the above four types are superimposed.

On the other hand, the cyan toner image is the toner material 20.
The second image forming station P while being transferred to
In b, a latent image of magenta component color is formed, and subsequently, a toner image by magenta toner is obtained by the developing unit 204b,
A magenta toner image is transferred by the transfer unit 205b of the second image forming station Pb to the sheet material 209 that has been transferred at the first image forming station Pb.

The main cause of the image deviation is the deviation of the image writing timing of each image forming station in the case of the top margin of FIG.
In the case of the left margin, it is the deviation of the writing timing of each image of each image forming station, that is, the scanning start timing in one scanning line, and in the case of the inclination deviation in the oblique direction in FIG. In the case of the angular deviation or the angular deviation of the rotation axis of the photosensitive drum, which is caused by the magnification error in FIG. 6D, the scanning line length due to the error ΔL in the optical path length from the scanning optical system of each image forming station to the photosensitive drum. It is due to the deviation of the size.

Therefore, in order to eliminate the above four types of deviations,
First, regarding the top margin and the left margin, the scanning amount of the scanning lines 102C, 102M, 102Y, and 102Bk is electrically adjusted to correct the deviation amount. For the magnification error deviation and tilt deviation, the mirrors 106, 1 of the folding mirrors in the optical path of each station
C-shaped mirror pair 106, 10 in which 07 is paired at a right angle
As shown in FIG. 7, the deviation amount can be corrected by independently adjusting 7 in the arrow E direction and the arrow F direction with respect to the apparatus main body. As adjustment means for making these adjustments,
Actuators 108 and 109 such as a linear step actuator having a step motor, which is a drive source that linearly moves step by step, are provided.

By driving the actuator 108 in the E1 direction, the mirror pairs 106 and 107 are moved to the E1 direction.
The photosensitive drums 201a, 20
By shortening the optical path length up to 1b, 201c, 201d and driving the actuator 108 in the E2 direction, the optical path length can be adjusted to be long. In this way, the scanning line 1 having a predetermined spread angle by adjusting the optical path length
The length of 02C, 102M, 102Y, and 102Bk can be changed from m0 to m1 as shown in FIG. 8A, for example.

When the actuator 109 is moved, or when the actuator 109 is moved, or when the actuator 109 is driven in the F1 direction, the scanning line m0 in FIG. 8B is changed to the scanning line m3. The tilt angle can be changed.

As described above, the mirror pair 106, 107 in which a pair of mirrors are installed at a substantially right angle is used as the optical scanning unit to the photosensitive drums 201a, 201b, 201c, 20.
By arranging in the optical path of 1d and adjusting the positions of the mirror pairs 106 and 107 by the actuator 108 or the actuator 109, the optical path length or the scanning line position can be adjusted independently. That is, the scanning line 10 imaged on the photosensitive drum is formed by moving the pair of mirrors 106 and 107 arranged in a V shape in the E direction.
Scanning lines 102C, 102M, 102Y, 10 without changing the positions of 2C, 102M, 102Y, 102Bk.
It is possible to correct only the optical path length of 2Bk, and by moving the mirror pairs 106 and 107 in the F direction, the image forming position on the photosensitive drum and The angle can be corrected.

In order to carry out the magnification error correction and the tilt correction independently of each other, FIG. 9 (FIG. 9 (a) perspective view, FIG. 9 (b))
As shown in the right side view and the left side view of FIG. 9C, the color misregistration correction device includes a mirror holding member (31) and a support member 1 (3).
2), the support member 2 (33) and the like. Therefore, it is configured to easily vibrate. Further, in an apparatus having a plurality of image carriers, generally, there are many vibration sources, and when a rotary polygon mirror, a drive system for moving a photoconductor or a transfer belt to form an image is moved, the vibration energy of the drive system is applied to the mirror. The position of the laser beam that is transmitted to the support portion and vibrates the device and is irradiated onto the drum also vibrates and appears as scanning unevenness.

Here, the cause of the vibration of the position of the laser beam will be described. FIG. 3 shows one of the image forming stations in the sectional view of FIG.

FIG. 3A shows a laser light source, a rotating polygon mirror,
The figure shows a case where the optical scanning unit 10 including the above components vibrates in the vertical direction due to the rotational imbalance of the rotating polygon mirror that rotates at high speed. Since the optical scanning unit 18 is fixed to the flat plate 1 of the apparatus, the flat plate vibrates in the gravitational direction in the upward and downward directions due to the weight of the optical scanning unit. When the optical scanning unit vibrates, the laser beam also vibrates vertically.
The oscillated laser beam is the above-mentioned V-shaped mirror pair 10
6, 107 and the reflection mirror 104 reflect the light and irradiate the drum. The laser beam applied to the drum vibrates geometrically simply by "1" when the optical scanning unit vibrates by "1".

Next, a case where the above-mentioned color misregistration correction device including the pair of V-shaped mirrors 106 and 107 vibrates is shown in FIG. Since the flat plate 1 vibrates vertically due to the imbalance of the rotary polygon mirror, the color misregistration correction device fixed thereto also vibrates vertically. As can be seen from the figure, when the pair of 90 ° mirrors vibrate "1" up and down, the laser beam applied to the drum vibrates geometrically "2". The actual vibration appears as a maximum vibration of "3" by combining "1" and "2" described above.

[0026]

As described above, since the conventional image forming apparatus has the color misregistration correction device including the pair of C-shaped mirror pairs, the vibration caused by the drive system such as the rotary polygon mirror is caused. There was a defect that the laser beam position vibrated and appeared as scanning unevenness.

[0027]

In order to solve the above-mentioned problems, the present invention provides a scanning unit for rotating and deflecting a laser beam emitted from a light source to scan a photosensitive member, and a laser beam emitted from the scanning unit. And a mirror unit consisting of a pair of right-angled mirrors that reflect in a direction opposite to the emitting direction,
A laser beam scanning device having: a first supporting member that supports the scanning unit; a second supporting member that supports the mirror unit and that is independent of the first supporting member;
And the first support member and the second support member are orthogonal to each other.

[0028]

1 and 2 are a perspective view and a sectional view of a laser beam scanning device according to an embodiment of the present invention. To simplify the description, only the optical scanning unit 10 including a laser light source, a rotary polygon mirror, and the second image forming station are shown and described. Of course, the same applies to the other three image forming stations.

An optical scanning unit 10 which deflects laser light from a laser light source by a rotary polygon mirror and linearly scans it at a constant speed by an f-θ lens system is positioned and fixed on an optical stay 1 arranged in a horizontal direction. There is. The optical stay 1 has a hole 1a so that the mirror unit 20 which is the color misregistration correction device including the pair of C-shaped mirrors can be arranged.
Is open. The optical stay 1 has a front plate 2 on both ends thereof,
The rear side plate 3 abuts vertically and is fixed with screws 4. Further, image forming stations are positioned on the front side plate 2 and the rear side plate 3.

The mirror unit 20 is attached to the stay 5, and the call attaching stay 5 is fixed to the L-shaped mounts 5F and 5R fixed to the front side plate 2 and the rear side plate 3, respectively, with screws from above the apparatus. In other words, the mirror unit 20 is held between the front side plate 2 and the rear side plate 3, but it can be easily attached and detached for maintenance or the like.

Due to its constitution, the mirror unit is fixed in such a manner that a part of the mirror pair is put in the hole 1a opened in the optical stay. The case where the optical stay 1 vibrates due to the vibration of the driving system such as the rotary polygon mirror as described above in such a configuration will be described.

The optical stay 1, the front side plate 2, and the rear side plate 3 cause film vibrations Y ₁ and Y ₂ in the directions in which they are most likely to vibrate. The vibration Y _{1 of the} optical stay vibrates the laser beam emitted from the optical scanning unit as in the conventional example. The vibration amount of the irradiation position on the drum surface due to the vibration is the same as the conventional example, "1".
Is.

Next, the vibration Y ₂ of the front side plate 2 and the rear side plate 3 vibrates the mirror unit 10 in the Y ₂ direction. The vibration of the laser beam in that case will be described. 2 in FIG.
_{Since the two} directions are perpendicular to the paper surface, even if the pair of C-shaped mirrors vibrate in the Y ₂ direction, the laser beam hardly vibrates. That is, in the conventional example, the “2” vibration of the laser beam as described above becomes “0” and only the “1” vibration of the laser beam due to the vibration of the optical unit described above.

Further, the optical stay 1 of the present invention has a large opening 1a and a peripheral edge 1b which is a free end, so that the optical stay 1 has a characteristic that it is easily vibrated. This peripheral portion vibrates at Y ₃ by the vibration energy of the rotating polygon mirror or the like. As a result, since the vibration energy is dissipated into heat energy, the vibration Y _{1 of the} entire optical stay ₁ also decreases, and the vibration of the laser beam “1” due to the vibration of the optical scanning unit further decreases.

[0035]

As described above, according to the present invention, the vibration of the mirror unit is eliminated by supporting the optical scanning unit and the mirror unit on independent supporting members which are orthogonal to each other, and the vibration of the optical unit is also reduced, so that the laser beam is reduced. The vibration of the irradiation position is drastically reduced, and it becomes possible to obtain a high-quality image without scanning unevenness.

[Brief description of drawings]

FIG. 1 is a perspective view of a laser beam scanning device according to an embodiment of the present invention.

2 is a side view of the device of FIG. 1. FIG.

FIG. 3 is a diagram for explaining vibration of a laser beam scanning device.

FIG. 4 is a side view of a conventional image forming apparatus.

FIG. 5 is a diagram showing an optical path of a conventional image forming apparatus.

6 is a diagram showing a tilt of a laser beam scanning line of the apparatus shown in FIG.

7 is a diagram showing the adjustment of the mirror unit of the apparatus of FIG.

8 is a diagram showing a tilt of a laser beam scanning line in the scanning of FIG.

FIG. 9 is a diagram showing adjustment of the scanning mirror unit of FIG. 5;

[Explanation of symbols]

 1 Optical stay 2 Front side plate 3 Rear side plate 4 Screw 5 Mirror unit stay 1a Opening 1b Opening peripheral edge 5F Mounting base 5R Mounting base 10 Scanning unit 20 Mirror unit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kunihiko Kitayama Kunihiko Kitayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Kazuyoshi Chihisa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Yoshinori Mochida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (2)

[Claims] 1. A scanning unit for rotating and deflecting a laser beam emitted from a light source to scan a photoconductor, and a pair of right-angle mirrors for reflecting the laser beam emitted from the scanning unit in a direction opposite to the emission direction. In the laser beam scanning device including the mirror unit, the first supporting member supporting the scanning unit and the second supporting member independent of the first supporting member supporting the mirror unit.
A laser beam scanning device, comprising: a supporting member, wherein the first supporting member and the second supporting member are orthogonal to each other. 2. The laser beam scanning device according to claim 1, wherein the first support member has an opening, and the mirror unit is in the opening.