JP2003140070A - Scanning optical device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning optical device and an image forming device of high image quality by suppressing the positional deviation of several scanning lines caused by a thermal expansion difference, etc., with a simple and easy constitution. SOLUTION: The device is provided with a housing 111 wherein all the scanning optical systems such as return mirrors 104a, 104b, 104c and 104d, scanning lenses 103a, 103b, 103c, 103d, 105a, 105b, 105c and 105d, etc., are mounted, and also, wherein deflectors 109 and 110 are arranged on the same plane.

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 having a function of forming an image on a transfer material (recording medium) such as a sheet, for example, a copying machine, a printer, or a facsimile apparatus. The present invention relates to a scanning optical device provided in these devices.

[0002]

2. Description of the Related Art A laser beam printer (L
In a scanning optical device for periodically deflecting a light beam used in a BP) or a digital copying machine, for example, by an optical deflector composed of a rotating polygon mirror (polygon mirror), light is modulated from a light source means in accordance with an image signal. Let it out, fθ
A scanning optical element (imaging element) having characteristics is focused in a spot on a surface of a recording medium (photosensitive drum) having photosensitivity, and the surface of the recording medium is optically scanned to record an image.

FIG. 4 is a schematic view of a main part of a conventional scanning optical device of this type.

In the scanning optical apparatus shown in FIG. 4, the divergent light beam emitted from the light source means 91 is made into a substantially parallel light beam by the collimator lens 92, and the light beam (light amount) is limited by the diaphragm 93 so as to be predetermined only in the sub-scanning direction. The light enters a cylinder lens (cylindrical lens) 94 having a refractive power. Then, the substantially parallel light beam incident on the cylinder lens 94 is directly emitted in the state of the substantially parallel light beam in the main scanning cross section, and is converged in the sub scanning cross section to be an optical deflector 95 composed of a rotary polygon mirror. The image is formed as a substantially linear image on the deflecting surface (reflecting surface) 95a.

The light beam deflected and reflected by the deflecting surface 95a of the optical deflector 95 is guided through the scanning optical element (fθ lens) 96 having the fθ characteristic onto the photosensitive drum surface 98 as the surface to be scanned. Light is emitted, and the optical deflector 95 is rotated in the direction of arrow A to optically scan the surface of the photosensitive drum 98 in the direction of arrow B. By this, an image is recorded on the photosensitive drum surface 98 which is a recording medium.

By the way, recently, a color image forming apparatus having a plurality of (for example, four) scanning optical devices has been proposed (Japanese Patent Laid-Open Nos. 6-183056 and 10-1862).
54 publication).

[0007]

However, the scanning optical device in the image forming apparatus of the prior art as described above requires the same number of rotating polygon mirrors, optical deflectors, and optical boxes as the number of photosensitive drums. The cost of the optical device is high, and cost reduction has been a problem.

Then, the positional deviation of a plurality of scanning lines occurs due to an error in mounting each scanning optical device to the image forming apparatus and a difference in thermal expansion, which causes a problem of deterioration of image quality.

The present invention has been made in order to solve the above-mentioned problems of the prior art. An object of the present invention is to suppress the positional deviation of a plurality of scanning lines caused by a difference in thermal expansion with a simple structure. A high quality scanning optical device and image forming apparatus are provided.

[0010]

In order to achieve the above object, according to the present invention, a light source section, a deflection scanning means having a rotary polygon mirror for deflecting and scanning a light beam from the light source section, and the deflection scanning. In a scanning optical device provided with a plurality of scanning optical means having an optical member group for condensing a light beam deflected and scanned by the means on a predetermined surface, a plurality of the scanning optical means are attached and the plurality of the deflecting means are provided. It is characterized by comprising a casing in which the scanning means is arranged on the same plane.

The light source unit having one or more light emitting points is 2
The deflection scanning means includes a rotary polygon mirror that deflects and scans the light beams from the two light source units.
Light beams emitted from two light source units are incident on and deflected by different surfaces of the rotary polygon mirror, and the light beams are passed through the two groups of optical member groups arranged substantially symmetrically with respect to the rotary polygon mirror. It is also preferable to guide light to a predetermined surface.

A folding member for folding the light beam deflected and scanned by the deflection scanning means toward the predetermined surface is provided in each of the plurality of optical member groups so that the arrangement intervals of the folding members are substantially equal and the folding member has the same structure. It is also preferable that the installation angle is set to be substantially equal to the light flux incident on the folding member.

It is also preferable that the housing is provided with a lid member for sealing the space on the side where the deflection scanning means is arranged.

It is also preferable that the spaces in which the plurality of deflection scanning means are arranged communicate with each other in the housing.

It is also preferable that the casing is a resin molded product.

The image forming apparatus includes the scanning optical device described above, and guides the light beams emitted from the scanning optical device to the corresponding image carrier surfaces to scan the image carrier. The toner image obtained by developing the electrostatic latent image formed on the image carrier is transferred to a transfer material.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions of the components described in this embodiment,
The material, the shape, and the relative arrangement of them should be appropriately changed depending on the configuration of the device to which the invention is applied and various conditions, and the scope of the invention is not limited to the following embodiments.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
2 is a schematic view showing an image forming apparatus according to the embodiment of FIG.

In FIG. 1, reference numeral 51 is a scanning optical device having a structure described later, and 1C, 1M, 1Y and 1BK are image bearing members arranged at equal pitches, each as a predetermined surface, and in this embodiment, they are photosensitive. It consists of a drum.

The image forming operation by the image forming means will be described below with reference to FIG.

In the present embodiment, the light fluxes (laser beams) LC and L each light-modulated based on the image information.
M, LY, and LBK exit the scanning optical device 51 and irradiate the corresponding photosensitive drums 1C, 1M, 1Y, and 1BK, respectively, to form electrostatic latent images.

This latent image is formed by the primary chargers 2C, 2M, 2
The toners of cyan, magenta, yellow, and black are formed on the surfaces of the photosensitive drums 1C, 1M, 1Y, and 1BK which are uniformly charged by Y and 2BK, respectively, and the developing devices 4C, 4M, 4Y, and 4BK respectively. A color image is formed by being electrostatically transferred to the transfer material P conveyed on the transfer belt 7 by the transfer rollers 5C, 5M, 5Y, and 5BK in order to be visualized as an image.

After that, the photosensitive drums 1C, 1M, 1Y, 1
The residual toner remaining on the BK surface is cleaned by the cleaners 6C and 6C.
The primary chargers 2C, 2M, 2Y, 2 are again removed by the M, 6Y, 6BK to form the next color image.
It is uniformly charged by BK.

The transfer materials P are stacked on a paper feed tray 21, and are sequentially fed one by one by a paper feed roller 22, and are registered on a transfer belt 7 by a registration roller 23 in synchronism with an image writing timing. Sent to.

While being accurately conveyed on the transfer belt 7, the cyan image, the magenta image, the yellow image, and the black image formed on the surfaces of the photosensitive drums 1C, 1M, 1Y and 1BK are sequentially transferred. The color image is formed by being transferred onto the material P.

The drive roller 24 accurately feeds the transfer belt, and is connected to a drive motor (not shown) with little rotation unevenness.

The color image formed on the transfer material P is heat-fixed by the fixing device 25, then conveyed by the paper discharge roller 26 and output to the outside of the apparatus.

FIG. 2 is a diagram for explaining the configuration of the scanning optical device according to the present embodiment, in which (a) is a schematic top view,
(B) is a schematic sectional drawing.

Semiconductor lasers 101a, 1 as a light source section
Beams (light fluxes) emitted from 01b, 101c, and 101d are rotary polygon mirrors 102 and 1 that constitute deflection scanning means.
It is incident on 08 different surfaces and is scanned in different directions.

The beams B1, B2, B3, B4 scanned by the rotary polygon mirrors 102, 108 pass through the first scanning lenses 103a, 103b, 103c, 103d, respectively, and have the same pitch as the photosensitive drum pitch. Folding mirrors 104a, 104b, 10 as folding members arranged at the same angle with respect to the incident light beam.
The direction is changed by α ° by 4c and 104d, and the second scanning lens 105a, 105b, 105c and 105d
Can be formed on the four photosensitive drums.
Here, the first scanning lenses 103a, 103b, 10
3c and 103d, folding mirrors 104a and 104b,
104c, 104d, second scanning lens 105a, 1
An optical member group is configured by 05b, 105c, and 105d.

The scanning optical device 51 includes a polygon mirror 10
Deflector 1 serving as a deflection scanning unit, which is provided with 2 and 108, respectively.
09 and 110 are provided on the same plane of one housing 111,
And other folding mirrors 104a, 104b, 1
04c, 104d and scanning lenses 103a, 103b, 1
03c, 103d, 105a, 105b, 105c, 1
By providing all of the scanning optical system (scanning optical means) such as 05d in a housing 111 molded of resin or the like, and sealing the space on the side of the rotary polygon mirror by a lid 112 as a lid member, noise and dirt can be prevented. Prevents entanglement.

With such a structure, the following effects can be obtained as compared with the case where a plurality of conventional scanning optical devices are used.

(1) Since only one housing is required, the structure is simplified, and the material cost and the molding cost can be reduced.

(2) Since the seating surfaces of the deflector and the scanning lens are formed in the same plane of the same housing, the precision can be easily obtained by molding. In addition, accuracy is easy to obtain when performing secondary processing.

(3) Since only one lid 112 is required, the structure is simplified, the assembling work to the housing is facilitated, and the number of parts of assembling means such as screws to the housing can be reduced.

(4) Since only one bar code label or laser caution label is required for manufacturing control, the number of parts can be reduced and work efficiency can be improved.

(5) Since the number of connecting means with the image forming apparatus is reduced, the structure is simplified and the assembling work efficiency is improved.

(6) It is possible to reduce the difference in the scanning spot diameter due to the positional deviation of the scanning lines among the plurality of scanning optical devices and the difference in thermal expansion.

As described above, according to the present embodiment, it is possible to reduce the number of housings, rotary polygon mirrors, optical deflectors, lids, etc., which were required in the past, so that the apparatus can be manufactured inexpensively and accurately. . Further, by including a plurality of scanning optical systems in the same housing, it is possible to reduce the positional deviation between the plurality of scanning optical systems and improve the image quality.

In this embodiment, the case where the semiconductor laser has one light emitting point has been described, but the same effect can be obtained even if a semiconductor laser having a plurality of light emitting points such as a multi-beam laser is used. it can.

(Second Embodiment) FIGS. 3A and 3B are views for explaining the configuration of a scanning optical device according to a second embodiment, where FIG. 3A is a schematic top view and FIG. It is a schematic sectional drawing. The same components as those described in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 3, the casing 113 connects the space around the deflectors 109 and 110 by removing the shield such as the rib between the deflectors 109 and 110.

With this configuration, the rotary polygon mirrors 102, 10 are operated when the motor is heated by driving the deflector or when the scanning optical device receives heat from the outside.
8, the first scanning lens 103a, 103b, 103
c, 103d, folding mirrors 104a, 104b, 1
The temperature difference between 04c and 104d can be reduced, and the thermal expansion difference between the optical elements can be reduced.

As a result, the scanned beams B1, B2
It is possible to suppress the positional deviation of B3 and B4, prevent the color deviation and the like, and improve the image quality.

[0045]

As described above, according to the present invention,
Since the deflection scanning means and the optical member group are formed in the same plane of the same housing, the precision can be easily obtained by molding, and a simple structure can be obtained because of the positional deviation of the scanning line between the plurality of scanning optical means and the difference in thermal expansion. The difference between the scanning spot diameters can be reduced, and a high-quality scanning optical device and image forming apparatus can be provided.

Further, since it is possible to reduce the number of housings, rotary polygon mirrors, deflection scanning means, lid members and the like, which are conventionally required in plural numbers, it is possible to provide an inexpensive scanning optical device having a simplified structure. .

Further, by connecting the spaces in which the plurality of deflection scanning means are arranged to communicate with each other, the temperature difference between the optical elements can be reduced, so that the difference in optical characteristics due to the difference in thermal expansion can be suppressed. As a result, it is possible to prevent the positional deviation of each light beam and improve the image quality.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an image forming apparatus provided with a scanning optical device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the configuration of the scanning optical device according to the first embodiment of the present invention, in which (a) is a schematic top view,
(B) is a schematic sectional drawing.

FIG. 3 is a schematic view showing a configuration of a scanning optical device according to a second embodiment of the present invention, (a) is a schematic top view,
(B) is a schematic sectional drawing.

FIG. 4 is a schematic view showing a scanning optical device according to a conventional technique.

[Explanation of symbols]

51 Scanning optical devices 101a, 101b, 101a, 101b Semiconductor lasers 102, 108 Polygon mirrors 103a, 103b, 103c, 103d First scanning lenses 104a, 104b, 104c, 104d Folding mirrors 105a, 105b, 105c, 105d Second sheets Scanning lenses 106, 113 housings 109, 110 scanner motors LC, LM, LY, LBK

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/113 H04N 1/04 104A (72) Inventor Yasutaka Naige 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akihiro Fukutomi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F-term (reference) 2C362 AA11 AA42 AA44 AA45 AA46 BA51 BA52 BA53 BA87 BA90 CA22 CA39 DA09 DA14 2H045 AA01 BA22 BA34 DA02 DA04 5C051 AA02 CA07 DA02 DB02 DB22 DB24 DB30 DC04 DC05 DC07 FA01 5C072 AA03 BA12 HA02 HA09 HA13 HA20 XA01 XA05

Claims (7)

[Claims] 1. A light source unit, a deflection scanning unit having a rotating polygon mirror for deflecting and scanning a light beam from the light source unit, and an optical member group for condensing a light beam deflected and scanned by the deflection scanning unit on a predetermined surface. A scanning optical device having a plurality of scanning optical means including: and a housing to which the plurality of scanning optical means are attached, and the plurality of deflection scanning means are arranged on the same plane. Scanning optics. 2. The light source section having one or more light emitting points is 2.
The deflection scanning means has a rotating polygon mirror that deflects and scans the light beams from the two light source units, and the light beams emitted from the two light source units are applied to different surfaces of the rotating polygon mirror. 2. The incident / deflection scanning is performed, and the light flux is guided to the predetermined surface through the two groups of optical members arranged substantially symmetrically with respect to the rotary polygonal mirror. Scanning optics. 3. A plurality of optical member groups are provided with folding members for folding the light beam deflected and scanned by the deflection scanning means toward the predetermined surface, and the arrangement intervals of the folding members are made substantially equal to each other.
The scanning optical device according to claim 1 or 2, wherein the installation angle of the folding member is arranged so as to be substantially equal to a light beam incident on the folding member. 4. The scanning optical device according to claim 1, wherein the housing is provided with a lid member for sealing a space on the side where the deflection scanning means is arranged. 5. The scanning optical device according to claim 1, wherein spaces in which a plurality of the deflection scanning units are arranged communicate with each other in the housing. 6. The scanning optical device according to claim 1, wherein the housing is a resin molded product. 7. A scanning optical device according to claim 1, further comprising a scanning optical device, wherein light beams emitted from the scanning optical device are guided to respective corresponding image carrier surfaces to carry the image carrier. An image forming apparatus characterized in that a body is scanned, and a toner image obtained by developing an electrostatic latent image formed on the image carrier is transferred to a transfer material.