JP2002341273A - Optical scanner and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly write images with respective light beams which are distributed by an optical deflector to scan an image carrier in opposite directions by preventing the individual light beams from having differences of shading characteristics (including droop characteristics), thereby obtaining improved picture quality. SOLUTION: When the light beams for respective color constitution colors are distributed by the optical deflector to LD1 and LD2, and LD3 and LD4, any of the beams which are divided into two is made incident on the optical deflector from a direction wherein the angle of incidence increases as the deflector rotates, and then even when scanning directions becomes opposite to each other, composite shading characteristics of both shading characteristics varying depending upon the angle of incidence and droop characteristics depending upon temperature cancel each other and become nearly flat. Consequently, images written by respective colors do not show differences between the distributed beams and density unevenness and color unevenness are eliminated even after the images are put one over the other.

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 which sorts a plurality of light beams by an optical deflector and scans an image carrier having a predetermined arrangement by the sorted light beams. In order to form a color image, a plurality of scanning light beams are used to write an image of each color component on the image carrier, and each written image is superimposed on a transfer material to form a color image. Difference in shading characteristics at the time of scanning each light beam, which causes deterioration in image quality when superimposed (due to droop characteristics (temperature characteristics) of light sources and differences in scanning mechanism)
The present invention relates to an image forming apparatus, such as a copier, a printer, a facsimile, a plotter, and the like, provided with the scanning device and the optical scanning device capable of performing high-quality image conversion while suppressing unevenness in the amount of light caused by the light scanning.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus (copier, printer, facsimile,
In a plotter, a tandem method is used in which a light beam is irradiated onto a surface to be scanned of a plurality of image carriers arranged in parallel to write a latent image. In an apparatus according to this method, light beams emitted from a plurality of light sources are applied to four image carriers (for example, photosensitive drums) arranged in parallel to write a latent image in a scanning manner. A latent image formed on the body is developed with a developer of a different color (for example, yellow, magenta, cyan, or black toner) to form a visible image, and then, a recording sheet carried on a transfer conveyance belt or the like The transfer material of each color is sequentially conveyed to the transfer portion of each image carrier, and the visible images of each color formed on each image carrier are superimposed and transferred on the transfer material, and then the image transferred on the transfer material is transferred. There is known an image fixing device for obtaining a multicolor image.

In such a tandem type color image forming apparatus, a type in which a latent image is written on each image carrier individually by an optical writing device provided for each image carrier is known. An optical writing device using an optical deflector composed of a mirror and a motor for driving the mirror is relatively expensive, and providing an individual optical writing device for each image carrier increases the cost of parts used and the manufacturing cost. There is a problem in that. Further, in order to install a plurality of optical writing devices each having an optical deflector in accordance with the number of image carriers, a large installation space is required, which causes a problem that the entire image forming apparatus becomes large. Therefore, in order to reduce the cost and size of the tandem type color image forming apparatus, as a means for performing optical writing on a plurality of image carriers, an optical deflector is commonly used for a plurality of light sources, In other words, an apparatus has been put into practical use in which light beams from a plurality of light sources are simultaneously deflected and scanned by a single optical deflector to irradiate a plurality of image carriers, thereby performing optical writing.

Such a conventional apparatus in which light beams from a plurality of light sources are simultaneously deflected and scanned by a single optical deflector to perform optical writing is arranged symmetrically in two directions about a single optical deflector. The optical deflector is provided with an optical system that guides light beams from a plurality of light source units that are deflected and scanned by a light deflector onto respective corresponding surfaces to be scanned, and forms all the components of an optical writing apparatus including these components in a single housing. As a result, the number of components can be reduced and the installation space can be reduced as compared with a conventional device having a plurality of optical writing devices, so that the cost and size of the image forming apparatus can be reduced. By the way, in the case of an image forming apparatus including the optical writing device having the above-described configuration and forming a full-color image, usually, as a plurality of light source units, a light source unit for black,
Three color light source units (for example, light source units for cyan, magenta, and yellow) are provided, and only the light source unit for black is used in the monochrome mode for forming a monochrome image. In the color mode, four light source units for black and color are used, and the light beams from the four light source units are simultaneously deflected and scanned by one optical deflector, and each of the four light beams is carried through an optical system. Light writing is performed by irradiating the body. When a latent image is formed by irradiating light to the four image carriers, a synchronization sensor is provided to match the writing position of light from each of the four light sources in the main scanning direction. The writing timing of each of the four colors is adjusted according to the output of the synchronous sensor.

Here, the writing scan by the light beams from the four light source units in the color mode in the above-described prior art will be described in more detail. FIG. 5 is a conceptual diagram showing how a light beam scans an image carrier by an optical deflector. In FIG. 5, light beams LD1, LD2, LD3, and LD4 from LD (Laser Diode: semiconductor laser) light sources of the four light source units act on the optical deflector, and the light beams that have been sorted out have image heights. Although the concept that the photosensitive member (photosensitive drum) is scanned in the direction of the arrow over 150 to +150 is shown, an optical writing device actually used for such an operation is shown in FIG. Be composed. In FIG. 8, light beams LD1, LD2, LD3, LD4
Are generated from the LDs of the four light source units 52 to 54,
After being sorted by the optical deflector 62, scanning writing is performed on a photosensitive drum (not shown) (for the optical writing device of FIG. 8, see FIGS. 1 and 3 showing an embodiment of the present invention).

Referring to FIG. 5, scanning writing on a photosensitive member will be described. Assuming that the horizontal and vertical axes passing through the center of the optical deflector are the X and Y axes, respectively, as shown in the figure, the light beams LD1 and LD2 from the LD units for two colors emit light in the second quadrant (light deflection in a horizontal plane). (A quadrant constituted by the center of the vessel and the X axis), and the other light beams LD3 and LD4 are arranged in the first quadrant. The rotation direction of the optical deflector is in the direction of the arrow (clockwise) in the figure around the Y axis. When the deflector rotates, L
The light beam emitted from the D unit scans each photoconductor in a certain direction through various lens systems. That is, as shown on the left side of FIG. 5, the light beams LD1 and LD2 have an image height of −150 → + 1.
The light beams LD3 and LD4 scan the photoconductors in the direction of 50, and in the direction of the image height + 150 → -150 in opposite directions, as shown on the right side of FIG. From the angle of incidence (0 ° <incident angle <60 °) on the light beam, the image height is roughly -150 →
The shading characteristic of 0 → + 150 (the characteristic that changes depending on the angle of incidence of the light beam on the optical deflector) is the light beam LD
1, LD2 and light beams LD3 and LD4 do not change with respect to the image height. In other words, all light beams are arranged such that the image height increases as the incident angle decreases (shading decreases). . FIG. 6 is a diagram illustrating the shading characteristics and the droop characteristics (described later) with respect to the image height. As shown in FIG. 6, the shading characteristic by this arrangement shows a characteristic that decreases almost linearly at an image height of −150 → 0 → + 150.

On the other hand, as a factor for changing the light amount of the light beam to be used, there is a droop characteristic (temperature characteristic) of the LD of the LD unit which is a light emitting source. Due to the droop characteristic, even during scanning of one line in the main scanning direction, the light emission amount decreases due to the light emission heat of the LD itself, and the light amount decreases considerably at the end of the scanning direction. The droop characteristic has such a property that the light beams LD1, LD2, the light beams LD3, LD4
Scan the photoreceptors in opposite directions, as described above, so that each will exhibit opposite slope characteristics, as shown by the dashed line in FIG. 6, which is high at the beginning of the scan and low at the end. . FIG. 7 shows the shading characteristics (characteristics that change according to the incident angle of the light beam on the optical deflector) and the effects of the droop characteristic, which appear as described above.
As shown in the figure, on the side of the light beams LD3 and LD4, one characteristic is dark on the image height +150 side and bright on the image height -150 side, whereas the other characteristic is bright on the image height +150 side and bright on the image height +150 side. Since the 150 side becomes darker, the two characteristics cancel each other out, and the combined shading characteristics become almost flat.

[0008]

However, as shown in FIG. 7, the combined shading characteristics of the light beams LD1 and LD2 both increase because the image height -150 is brighter and the image height +150 is darker. Resulting in. As described above, when the light beam is written by the arrangement shown in FIG. 5, the light beams LD1 and LD2 are written.
A difference occurs in the combined shading characteristics of the light beams LD3 and LD4.
For example, when the color of the light beam LD3 and the color of the light beam LD3 are superimposed on each other, a difference occurs in the amount of writing light that should be performed with an appropriate amount of light according to the same characteristic, resulting in a change in tint and a deterioration in image quality. . The present invention has been made in view of the above-mentioned problems of the related art in an optical scanning device that sorts a plurality of light beams by an optical deflecting unit using a rotating reflection surface and scans an image carrier having a predetermined arrangement by the sorted light beams. The purpose of the method is to prevent a difference in shading characteristics (including characteristics that change according to the incident angle of the light beam on the light deflecting means and droop characteristics) of each of the divided light beams. Provided is an optical scanning device capable of appropriately performing image conversion by each light beam on an image carrier, improving image quality, and being applicable to writing of a color image, and an image forming apparatus including the optical scanning device. Is to do.

[0009]

According to a first aspect of the present invention, a plurality of light beams are distributed by an optical deflecting means using a rotating reflection surface, and some of the divided beams scan an image carrier having a predetermined arrangement. A light scanning device that scans the image carrier from a direction opposite to the direction,
An optical scanning device wherein the light beam is incident from a direction in which the incident angle of the light beam on the rotary reflecting surface of the light deflecting means increases with rotation. .

According to a second aspect of the present invention, in the optical scanning device according to the first aspect, the plurality of light beams carry an image to be written, and the image carrier is a photosensitive member. It is characterized in that optical writing is performed on the.

According to a third aspect of the present invention, in the optical scanning device according to the second aspect, each of the plurality of light beams has an image corresponding to a constituent color of a color image. It is.

According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising the optical scanning device according to any one of the first to third aspects.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical scanning device and an image forming apparatus according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of an optical writing device as one embodiment according to the optical scanning device of the present invention, and FIG.
1 is a schematic configuration diagram illustrating an example of an image forming apparatus including the optical writing device illustrated in FIG. FIG. 3 is a plan view showing the configuration of the optical writing device shown in FIG. 1 on the upper surface side of the substrate. In addition,
FIG. 1 shows a cross-sectional configuration taken along line AA ′ of FIG. Hereinafter, the configuration, operation, and operation of the optical writing device and the image forming apparatus according to the present embodiment will be described in detail with reference to FIGS. First, before describing the optical writing device, an outline of an image forming apparatus using the optical writing device will be described. As shown in FIG. 2, the image forming apparatus is a full-color image in which a plurality of drum-shaped photoconductive photoconductors (hereinafter, referred to as “photoconductor drums”) 1, 2, 3, and 4 are arranged as a plurality of image carriers. Forming the four photosensitive drums 1, 2, 2
For example, yellow (Y), magenta (M), cyan (C), black (B
k) to form an image corresponding to each color (note that
The order of the colors is not limited to this, and can be set arbitrarily.) Around each of the four photosensitive drums 1, 2, 3, 4, a charging unit (a charging roller, a charging brush, a charging charger, etc.) 6, 7, 8, for forming an image by an electrophotographic process. 9, an exposure unit of the light beams L1, L2, L3, and L4 from the optical writing device 5, and a development unit (Y,
M, C, and Bk developing devices) 10, 11, 12, 1
3, transfer means (transfer rollers, transfer brushes, etc.) 14, 15, 1
Transfer / transport device 22 provided with cleaning devices 6 and 17, and cleaning unit (cleaning blade, cleaning brush, etc.) 1
8, 19, 20, 21 and the like are provided, and each of the photosensitive drums 1, 2, 3, and 4 can form an image of each color.

The optical writing device 5 is disposed obliquely above an image forming unit in which four photosensitive drums 1, 2, 3, 4 are arranged side by side, and an image is formed by a main reference pin Pa and a sub reference pin Pb on the housing side. It is positioned and fixed on the main body frame 29 of the forming apparatus. The top view of the frame 29 is shown in FIG. 3, in which the housing main reference pin Pa side is a decision hole (round hole) and the slave reference pin Pb side is an elongated hole. The optical writing device 5 includes four light source units 5 as shown in FIGS.
2, 53, 54, and 55, the light beams LD1, LD2, LD3, and LD4 from each light source unit are distributed in two symmetrical directions, and an optical deflector 62 as an optical deflector for deflecting and scanning, and an optical deflector 62 And a plurality of light beams LD1, LD2, LD3, and LD4 that are deflected and scanned by the optical deflector 62. Optical systems (imaging lenses 63, 64, 69, 70, 71, 72, mirrors 65 for turning back the optical path, 66, 67, 68, 73, 7
4, 75, 76, 77, 78, 79, 80, etc.), and these components are housed in one housing 50. More specifically, the housing 50 has a base 50A on which the optical deflector 62 and the optical system are disposed, and a frame-shaped side wall 50B surrounding the periphery of the base 50A. , And is a structure that partitions the housing 50 up and down,
The four light source units 52, 53, 54, and 55 are disposed on the side wall 50B of the housing 50, and the optical deflector 62 is disposed substantially at the center of the base 50A of the housing 50. 50A are provided separately on both surfaces (upper surface side and lower surface side). Further, covers 87 and 88 are provided on the upper and lower portions of the housing 50, and an opening for passing a light beam is provided on the lower cover 87, and dustproof glass 83, 84, 85,
86 is attached.

The optical writing device 5 converts color-separated image data input from a document reading device (scanner) (not shown) or an image data output device (personal computer, word processor, facsimile receiving section, etc.) into a signal for driving a light source. The light beams emitted from each of the light source units 52, 53, 54, 55 are converted into cylindrical lenses 56, 57, 57
After passing through 58 and 59, the light reaches a light deflector 62 directly or via mirrors 60 and 61, and is deflected and scanned in two symmetrical directions by two-stage polygon mirrors 62a and 62b rotated at a constant speed by a polygon motor 62c. . In the configuration shown in FIG. 1, the polygon mirrors are used for the light beams L2 and L3,
Although the configuration is divided into upper and lower stages for the light beams of L1 and L4, a configuration in which four light beams are deflected and scanned by one thick polygon mirror may be used. The light beams deflected and scanned by the polygon mirrors 62a and 62b of the light deflector 62 in two directions, two beams at a time, pass through first imaging lenses 63 and 64 each composed of, for example, an upper and lower two-layer fθ lens. After being folded by the first folding mirrors 65, 66, 67, 68 and passing through the opening of the base 51, the second imaging lenses 69, 70, 71, 72 composed of, for example, a long toroidal lens (WTL) are moved. After passing through, the second folding mirrors 73, 75, 77, 79, the third folding mirrors 74, 76, 78, 80, the dustproof glass 83, 84, 8
5, 86 through the photosensitive drums 1, 2, 3, 4 for each color
Irradiates an electrostatic latent image on the surface to be scanned.

In the above-described optical writing device 5, the four light source units 52, 53, 54 and 55 are composed of a semiconductor laser (LD) as a light source and a collimating lens for collimating the emitted light beam of the semiconductor laser. The light source unit for black (for example, the light source unit denoted by reference numeral 54), which is often used when forming a black-and-white image, has two or more light sources (for example, light source unit 54). LD) and a collimating lens. In the case of a multi-beam configuration, the side wall 50 of the housing 50
If the light source unit is configured to be rotatable about the optical axis with respect to B, the beam pitch in the sub-scanning direction can be adjusted, and the pixel density (for example, 600 dpi,
1200 dpi). Further, in the optical path of each light beam L1, L2, L3, L4,
A synchronization detecting mirror (not shown) for taking out the light beam at the scanning start position in the main scanning direction is provided. The light beam reflected by the synchronization detecting mirror is received by the synchronization detectors 81 and 82 to synchronize the scanning start. A signal is output.

The scanning direction of the light beam deflected and scanned by the optical deflector 62 is the main scanning direction, which is the axial direction of each of the photosensitive drums 1 to 4. The direction orthogonal to the main scanning direction is the sub-scanning direction.
4 to the rotation direction (moving direction of the photosensitive drum surface), and furthermore, the transfer direction of the transfer transfer belt 22a described later. That is, the width direction of the transfer conveyance belt 22a is the main scanning direction, and the conveyance direction is the sub-scanning direction. As shown in FIG. 2, below the four photoconductor drums 1, 2, 3, and 4 arranged side by side, a transfer roller 22a stretched over a driving roller and a plurality of driven rollers is disposed. It is conveyed by a driving roller in the direction indicated by the arrow in the figure. Further, a plurality of paper feed units 23 and 24 containing transfer materials such as recording paper are installed in the lower part of the main body of the image forming apparatus.
The transfer material stored in the transfer transfer belt 22a is transferred to the transfer transfer belt 22a via a feed roller, a transfer roller, and a registration roller 25.
And is carried and transported by the transfer / transport belt 22a. Each latent image formed on each of the photosensitive drums 1, 2, 3, and 4 by the above-described optical writing device 5 is transferred to each of the developing units
0, 11, 12, and 13 are developed with toners of respective colors of Y, M, C, and Bk and visualized, and the visualized Y, M, and
The toner images of the respective colors of C and Bk are sequentially superimposed and transferred onto the transfer material carried on the transfer / conveyance belt 22a by the transfer means 14, 15, 16, 17 of the transfer / conveyance device 22. The transfer material onto which the four color images have been transferred is conveyed to a fixing device 26, where the image is fixed by the fixing device 26, and then discharged onto a discharge tray 28 by a discharge roller 27.

The basic structure and operation of the optical writing apparatus and the image forming apparatus according to the present invention have been described above.
In the optical writing device 5 according to the present invention, the housing 50
Is a base 50A on which the optical deflector 62 and the optical system are disposed,
A frame-shaped side wall 50B surrounding the periphery of the base 50A, and the base 50A is provided at a substantially central portion of the side wall 50B to partition the housing 50 up and down. The four light source units 52, 53, 54, 55 Is disposed on the side wall 50B of the housing 50, and the optical deflector 62 is disposed substantially at the center of the base 50A of the housing 50, and optical members (imaging lenses 63, 64, 69, 70, 7) constituting an optical system are formed.
1, 72, mirrors 65, 66, 67 for turning back the optical path,
68, 73, 74, 75, 76, 77, 78, 79, 8
0) are arranged separately on both sides (upper surface side and lower surface side) of the base 50A, so that the size of the housing 50 of the optical writing device 5 is reduced while ensuring the entire optical path length of the optical system. , The optical writing device 5 can be made more compact. Further, in the image forming apparatus having the configuration shown in FIG.
The image forming unit in which 3 and 4 are arranged side by side, the optical writing device 5 and the transfer / conveying device 22 are compactly housed in the image forming apparatus main body, and are further installed obliquely with respect to the horizontal direction (X direction in the figure). Therefore, the installation space can be reduced as compared with the conventional horizontal arrangement, and the tandem-type color image forming apparatus can be further reduced in size.

Here, the writing performance related to the shading characteristics of the optical writing device 5 will be described in detail. A light beam from the light source unit (a light beam carrying images corresponding to the four constituent colors of the color image) is distributed by an optical deflector 62 using a polygon mirror, and light is written on the photosensitive drums 1, 2, 3, and 4. When the above-described method is adopted, the scanning directions of the divided beams are opposite. Here, depending on the relationship between each of the allocated light beams and the optical deflector, as described in the above section of the "prior art", the shading characteristics of each of the allocated light beams (the incident angle of the light beam to the light deflecting means depends on the incident angle). (Including the changing characteristics and droop characteristics), resulting in deterioration of image quality. According to the present invention, the light beams are distributed by the optical deflectors so that no difference occurs in the shading characteristics of the divided light beams even when the scanning directions of the beams are opposite. For this purpose, in the present embodiment, the four light source units 52 to 54 of FIG.
As shown in the relationship 2, each of the divided light beams has a relationship in which the light beam is incident from a direction in which the angle of incidence on the rotary reflecting surface of the optical deflector increases with rotation (see FIG. 8 conventional example).

Hereinafter, shading characteristics by light beam scanning according to the present embodiment will be described. FIG. 4 is a conceptual diagram (A) showing a state in which a light beam scans an image carrier by an optical deflector and a shading characteristic, and a diagram showing each light beam in which the shading characteristic and the droop characteristic with respect to the image height are allocated ( B) and (C). FIG.
The scanning writing on the photoconductor will be described with reference to FIG. The horizontal and vertical axes passing through the center of the optical deflector
As shown in the drawing, when the X and Y axes are set, the light beams LD1 and LD2 from the LD units for two colors are arranged in a third quadrant (a quadrant constituted by the center of the optical deflector and the X axis in a horizontal plane). ,
Other light beams LD3 and LD4 are arranged in the first quadrant. The rotation direction of the deflector is in the direction of the arrow (clockwise) in the figure around the Y axis. Accordingly, each light beam and the light deflector have a relationship such that the incident direction of the light beam becomes larger as the angle of incidence on the rotary reflecting surface of the light deflector increases with rotation. Here, when the optical deflector rotates, the light beam emitted from the LD unit scans each photoconductor in a certain direction through the above-described optical system. That is, as shown on the left side of FIG. 4A, the light beams LD1 and LD2 are in the direction of the image height from -150 to +150, and the light beams LD3 and LD4 are on the right side of FIG. As shown in (2), the photoconductor is scanned in the direction of the image height + 150 → −150 in the directions opposite to each other. From the angle of incidence on the optical deflector (0 ° <incident angle <60 °), the shading characteristics of the image height -150 → 0 → + 150 (depending on the angle of incidence of the light beam on the optical deflector) The changing characteristics are that the light beams LD1 and LD2 have a larger incident angle toward the image height, whereas the light beams LD1 and LD2 have
Since the incident angle of LD3 and LD4 decreases in the image height direction, the shading characteristics of the former rise almost linearly from -150 to 0 to +150 as shown in Fig. 4B. In the latter case, as shown in FIG.
→ At +150, the characteristics decrease almost linearly.

Further, as a factor for changing the light amount of the light beam to be used, there is a droop characteristic (temperature characteristic) of the LD of the LD unit which is a light emitting source. Due to the droop characteristic, even during scanning of one line in the main scanning direction, the light emission amount decreases due to the light emission heat of the LD itself, and the light amount decreases considerably at the end of the scanning direction. The droop characteristic has such a property that the light beams LD1, LD2, the light beams LD3, LD4
Scans the photoconductors in opposite directions as described above, so that the former has an image height of -150 → 0 as shown in FIG.
→ The characteristic decreases almost linearly at +150, and the latter is shown in FIG.
As shown in (C), the image has a characteristic of increasing almost linearly at an image height of −150 → 0 → + 150. As described above, the shading characteristic (the characteristic that changes depending on the incident angle of the light beam with respect to the optical deflector) and the droop characteristic are opposite characteristics in the present embodiment, and are shown in FIGS. 4B and 4C. As described above, the combined shading characteristics of the two characteristics cancel each other, and as a result, there is no change in the light amount in the main scanning direction, and the characteristics become almost flat. Therefore, even if the scanning directions of the beams are opposite, no difference occurs in the combined shading characteristics of the divided light beams, so that when forming an image in the tandem method, the divided light beams form the color constituent colors. Even if the image is written and the written images of the respective colors are superimposed, the occurrence of density unevenness and color unevenness is reduced,
Image quality can be improved.

[0022]

(1) Effects corresponding to the first aspect of the invention All of the light beams distributed by the light deflecting means are made to enter from a direction in which the angle of incidence on the light deflecting means increases with rotation. (By arranging the LD unit on the scanning start side with respect to the rotation direction of the light deflecting means), even if the scanning directions of the divided beams become opposite, the combined shading characteristics of each of the divided light beams. Therefore, no mismatch occurs between the converted images. For example, even when the superimposition processing is performed using each converted image, the occurrence of light amount unevenness due to a difference in characteristics is reduced, and it is possible to prevent the image quality of the processed image from deteriorating. (2) Effects corresponding to the second and third aspects of the invention In addition to the effects of the above (1), an image is formed by a tandem system by applying light to a photoreceptor and applying to a color image. Even when the image is written with the divided light beams and the written images are superimposed, as in the case of using for optical writing at the time,
The occurrence of density unevenness and color unevenness is reduced, and image quality can be improved. (3) Effects corresponding to the fourth aspect of the invention The effects (1) and (2) can be realized in an image forming apparatus such as a copying machine, a printer, a facsimile, a plotter, etc., and the performance of the image forming apparatus is improved. It becomes possible to do.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an optical writing device as one embodiment according to an optical scanning device of the present invention.

FIG. 2 is a schematic configuration diagram illustrating an example of an image forming apparatus including the optical writing device illustrated in FIG.

FIG. 3 is a plan view illustrating a configuration of a top surface side of a substrate of the optical writing device illustrated in FIG. 1;

FIG. 4 shows a conceptual diagram (A) showing a state in which a light beam distributed by an optical deflector scans an image carrier, and diagrams (B) and (C) showing shading and droop characteristics.

FIG. 5 is a conceptual diagram showing a state in which a light beam distributed by an optical deflector scans an image carrier in a conventional technique.

FIG. 6 is a diagram showing shading characteristics and droop characteristics with respect to an image height in the conventional technique shown in FIG.

FIG. 7 is a conceptual diagram showing a state in which a light beam distributed by an optical deflector scans an image carrier in the related art shown in FIG.

FIG. 8 shows an example of an optical writing device using the conventional technique shown in FIG.

[Explanation of symbols]

1, 2, 3, 4 ... photosensitive drum, 5 ... optical writing device, 52, 53, 54, 55 ... light source unit, 62 ...
Optical deflector, 62a, 62b ... polygon mirror,
L1, L2, L3, L4... Light beams.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/23 103 H04N 1/04 104A F-term (Reference) 2C362 AA07 AA10 AA68 BA04 BA50 BA51 BA53 2H045 AA01 BA22 BA34 CB33 CB35 2H108 GA02 5C072 AA03 BA04 DA04 DA21 HA02 HA06 HA08 HA13 HB08 HB13 QA14 UA02 XA05 5C074 AA08 BB03 CC22 CC26 DD09 EE02 FF05 FF15 GG04 HH04

Claims (4)

[Claims] 1. A method according to claim 1, wherein a plurality of light beams are distributed by an optical deflecting means using a rotating reflection surface, and a part of the divided beams is scanned in an image carrier having a predetermined arrangement. An optical scanning device that scans an image carrier from a direction opposite to a direction, wherein a direction in which an incident angle of the light beam of the part and the other part on the rotary reflecting surface of the light deflecting unit increases with rotation. An optical scanning device characterized in that a light beam is made to enter from above. 2. The optical scanning device according to claim 1, wherein the plurality of light beams carry an image to be written,
An optical scanning device, wherein the image carrier is a photoconductor so that optical writing is performed on the image carrier. 3. An optical scanning device according to claim 2, wherein each of said plurality of light beams carries an image corresponding to a constituent color of a color image. 4. An image forming apparatus comprising the optical scanning device according to claim 1.