JPH11326798A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of making image quality higher by smoothly reproducing the edge part of an image even by inexpensive and simple constitution without making resolution high. SOLUTION: Two semiconductor lasers exposing the same pixel are provided in an exposure scanning part, and set so that the diameter of a beam spot 20b emitted from either semiconductor laser and formed into an image on a photoreceptor drum may be larger than the diameter of a beam spot 20a emitted from the other semiconductor laser and formed into the image on the photoreceptor drum and further the peak of the beam intensity of the beam spot 20b may be smaller than the peak of the beam intensity of the beam spot 20a.

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 copying machine or a printer, and more particularly, to a technique for exposing and scanning a photosensitive member by combining two light beams.

[0002]

2. Description of the Related Art In recent years, in image forming apparatuses such as copiers and printers, in order to meet demands for colorization and systemization, a semiconductor laser is driven based on image data to expose and scan a photosensitive drum. 2. Description of the Related Art Digital image forming apparatuses that form an image by developing an electrostatic latent image formed by toner with toner are becoming widespread.

[0003] In such a digital image forming apparatus, an electrostatic latent image is formed by exposing a photosensitive drum on a pixel-by-pixel basis with a laser beam emitted from a semiconductor laser. . FIG. 14 is a diagram showing an electrostatic latent image 29 formed on the photoconductor drum when eight pixels continuous in the sub-scanning direction are exposed by a laser beam, and the exposure intensity is measured from the center of each pixel. The state of decreasing with distance is shown by three levels of density change.

Since the beam spots corresponding to the respective pixels are circular, they are overlapped with each other to form a range in which the exposure intensity is developable, that is, in a portion where the toner adheres, a depression 291 is inevitably generated, whereby the edge portion is jagged. And the reproduced image deteriorates. This problem can be alleviated slightly by increasing the beam intensity to increase the spot diameter and widening the overlapping area of the beam between pixels, but this method also increases the spot diameter in the main scanning direction in the figure. As a result, the exposure intensity range that can be developed is increased, so that the line becomes thicker and the fine line reproducibility deteriorates.

Therefore, a special semiconductor laser (for example, such as a semiconductor laser) capable of changing the beam diameter in only one direction by adding a control current (beam diameter control current) different from the output control current.
A technique for smoothing an edge portion has been developed using Japanese Patent Application Laid-Open No. 7-89131 (O plus).
E. FIG. May 1996). According to this technique, pixels constituting an edge portion in image data are determined in advance, and the beam spot diameter at the time of exposing the determined pixel is changed so that the edge portion becomes smooth. According to this method, the reproducibility of the edge portion can be improved without unnecessary thickening of the line.

[0006]

However, in the above-described method of changing the beam spot diameter in one direction, a discriminating unit for discriminating image data corresponding to an edge is required in addition to an expensive semiconductor laser. Becomes complicated. Particularly, when drawing an edge portion extending in an oblique direction, it is necessary to change the beam spot diameter for each pixel according to the inclination, and high-speed data processing is required. Expensive materials with high processing power had to be used.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to provide an image forming apparatus capable of smoothly reproducing an edge portion of an image with an inexpensive and simple configuration. And

[0008]

According to the present invention, there is provided an image forming apparatus for forming an image by scanning an image carrier with a light beam based on pixel data.
The light beam is formed by combining a first light beam with a second light beam having a larger spot diameter and a smaller peak intensity on the image carrier than the first light beam. It is characterized by.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a light beam scanning apparatus according to the present invention will be described for a case where the light beam scanning apparatus is used in a full-color laser beam printer (hereinafter simply referred to as "printer"). (1) Overall Configuration of Printer FIG. 1 is a schematic diagram showing the overall configuration of the printer 1.

As shown in FIG. 1, the printer 1 forms an image by a well-known electrophotographic method, and is roughly divided into an exposure scanning section 10 and an image forming section 50. The printer 1 is connected to an external computer or the like (not shown), and the control unit 100 reproduces cyan (C), magenta (M), yellow (Y), and black (Bk) sent from the external computer. When an image signal for each color is received, necessary processing is performed to generate image data. These image data are converted into driving pulses of the semiconductor laser of the exposure scanning unit 10 and output to the semiconductor laser for each reproduced color. The semiconductor laser receiving the drive signal from inside the control unit 100 emits a laser beam corresponding to the image data. The laser beam is exposed and scanned in the main scanning direction on the peripheral surface of the photosensitive drum 61 via optical elements such as various lenses and folding mirrors to form an electrostatic latent image for any reproduced color. The configuration of the exposure scanning unit 10 will be described later.

The image forming unit 50 includes a photosensitive unit 60 including a photosensitive drum 61 and a full-color developing unit 70.
, An intermediate transfer unit 80 having an endless transfer belt 81, a paper feed unit 90 for feeding the recording sheet S, and the like. Before the photosensitive drum 61 receives the above-mentioned exposure, the residual toner on the surface thereof is removed by a blade 63 provided on a cleaner 62, and the photosensitive drum 61 is uniformly charged by a roller-shaped charging brush 64. When receiving exposure while being rotated in the direction of arrow a in the state of being charged
An electrostatic latent image is formed on the surface of the photosensitive drum 61.

The full-color developing unit 70 contains a developer containing toner of each of the reproduction colors of cyan (C), magenta (M), yellow (Y), and black (Bk).
The two developing units 71C to 71Bk are integrally mounted on a developing rack (not shown), and can be rotated clockwise in FIG. The control unit 100 controls the developing rollers 72C to 72B of the corresponding developing units 71C to 71Bk in accordance with the timing at which the electrostatic latent images of the respective reproduction colors are formed on the photosensitive drum 61.
The full-color developing unit 70 is rotated so that k is located at a developing position facing the photosensitive drum 61. As a result, the electrostatic latent image on the photosensitive drum 61 is developed, and a toner image of a reproduced color is formed.

The transfer belt 81 of the intermediate transfer unit 80
Is suspended by a drive roller 82, a support roller 83, a primary transfer roller 84, and the like, and is rotated in the direction of arrow b in synchronization with the photosensitive drum 61. Primary transfer roller 84
Is disposed at a position facing the photosensitive drum 61 via the transfer belt 81, and a voltage having a polarity opposite to the charged polarity of the toner is applied to the toner image formed on the photosensitive drum 61. The image is transferred onto the transfer belt 81. At this time, the image forming operation of each reproduced color on the photosensitive drum 61 is executed at such a timing that the toner image of each color is transferred to the same position on the transfer belt 81. This allows
The toner images of the respective reproduced colors are sequentially superimposed on the transfer belt 81 to form a full-color toner image.

On the other hand, below the support roller 83, a secondary transfer roller 86 is provided via a transfer belt 81 so as to be able to freely contact and separate from the transfer belt 81 by an urging mechanism (not shown). When a full-color toner image is formed on the transfer belt 81, the secondary transfer roller 86 is pressed against the transfer belt 81 by an urging mechanism, and is supplied with a voltage having a polarity opposite to the charging polarity of the toner. The full-color toner image on the transfer belt 81 is transferred onto the recording sheet S fed from the paper unit 90.

A paper supply unit 90 includes a paper supply tray 91 that can be opened and closed on the front side (the left side in FIG. 1) of the main body of the printer 1 and a paper supply cassette 92 that can be pulled out and stored on the front side.
Is provided. The recording sheet S set on the paper feed tray 91 or stored in the paper feed cassette 92 is fed to the timing roller 94 by the rotation of the paper feed roller 93, and a full-color toner image is formed on the transfer belt 81. In synchronization with the operation, the sheet is sent to the secondary transfer roller 86 by the timing roller 94.

The recording sheet S to which the full-color toner image has been transferred is conveyed to a fixing section 96 by a conveying belt 95, where it is heated and pressed to fuse and fix the toner on the surface of the recording sheet S. The sheet is discharged to the upper surface of the printer 1 by the discharge roller 99. (2) Configuration of Exposure Scanning Unit 10 FIG. 2 is a diagram showing a configuration of the exposure scanning unit 10 of FIG.
The exposure scanning unit 10 is driven by a polygon motor (not shown) to rotate at a constant speed in the direction of arrow c.
5, a light source device 11 including semiconductor lasers LD1 and LD2, a scanning lens 16 including a toroidal lens and an fθ lens, a folding mirror 17, and the like.

The light source device 11 includes two semiconductor lasers LD.
1, an LD 2, a beam splitter 13 holding a semipermeable membrane 131 therein, a collimator lens 14, and the like. The semiconductor lasers LD1 and LD2 receive a drive signal corresponding to pixel data from the control unit 100, and
8a and 18b are simultaneously injected. The laser beam 18a emitted from the semiconductor laser LD1 enters the beam splitter 13, passes through the semi-permeable film 131, and goes straight. On the other hand, the laser beam 1 emitted from the semiconductor laser LD2
8b enters the beam splitter 13 from a direction orthogonal to the optical axis of the laser beam 18a, is reflected by the semi-permeable film 131, and travels with its optical axis aligned with the optical axis of the laser beam 18a. . As described above, the laser beams 18a and 18 having the same optical axis via the beam splitter 13 are provided.
b (hereinafter, referred to as a “combined beam 18 c”) passes through the collimator lens 14 and is converted into a parallel light beam. Then, the light beam b is reflected and deflected by the mirror surface of the polygon mirror 15, and passes through the scanning lens 16 and the return mirror 17. The photosensitive drum 61 is exposed and scanned.

FIG. 3 is a view showing the shape of a beam spot 20 formed when the photosensitive drum 61 is exposed by one pixel (dot) with the combined beam 18c. The beam spot 20 is formed by overlapping a beam spot 20a formed by the laser beam 18a and a beam spot 20b formed by the laser beam 18b, and has a dot pitch d (between the center points of adjacent dots). At a resolution of, for example, 400
Approximately 64 μm for dpi. In the present embodiment, the pitch in the main scanning direction and the pitch in the sub scanning direction are the same. )
The beam spot 20b has a diameter approximately 1.5 times that of
It has approximately three times the diameter. Here, beam spot 2
The diameters of 0a and 20b are indicated by the diameters of the cross sections at a value of 1 / e ² of the peak value of the beam intensity distribution 21 (see FIG. 8) in the beam spot 20.

FIG. 4 is a plan view showing the structure of the light source device 11. The light source device 11 includes semiconductor lasers LD1, LD
2, holding members 31 and 32, and holding members 3 respectively.
It comprises support bases 33 and 34 for supporting the first and the second 32, a beam splitter 13, a cylindrical member 141 for holding the collimator lens 14, and a base 30 for holding these members.

The support bases 33 and 34 are both L-shaped, and extend in the direction perpendicular to the optical axes of the laser beams 18a and 18b, respectively, and extend along the optical axes of the laser beams 18a and 18b. The laser adjusting units 332 and 342 extend in parallel with each other. The holding members 31 and 32 are provided on a surface 3 perpendicular to the optical axis of the laser beams 18a and 18b, respectively.
At 11 and 321, they are in contact with the laser supports 331 and 341 and are attached at positions where both beams pass through the beam splitter 13 and are combined on the same optical axis.

The laser adjusting units 332 and 342 of the support bases 33 and 34 respectively control the laser beams 18a and 18a.
The surfaces 30a and 30b parallel to the optical axis b are in contact with the base 30, and are moved in directions (arrow directions) parallel to the optical axes to adjust the distance from the semiconductor lasers LD1 and LD2 to the beam splitter 13. (Focus adjustment). This focus position adjustment is realized by a known position adjustment mechanism, for example, by holding the support bases 33 and 34 on the base 30 so as to be slidable in the respective optical axis directions, and adjusting the position using precision screws. it can.

In such a configuration, first, focusing is performed by adjusting the position of the support base 33 so that the diameter of the beam spot 20a is approximately 1.5 times the dot pitch. Then, the position of the support base 34 is adjusted so that the diameter of the beam spot 20b becomes approximately three times the dot pitch. In this embodiment, in order to reduce the cost, the semiconductor lasers LD1 and LD2 having the same specifications are caused to emit light with the same drive current in the control unit 100 described later, so that the diameter of the beam spot 20b is changed to the diameter of the beam spot 20a. The distance from the semiconductor laser LD2 to the beam splitter 13 is set to be slightly longer than the distance from the semiconductor laser LD1 to the beam splitter 13 so that the focal position is shifted to form a blurred spot image. I have to.

Next, the configuration of the control unit 100 will be described with reference to FIG. As shown in FIG.
U101, LD1 drive circuit 102, LD2 drive circuit 10
3, ROM 104, RAM 105 and the like.
The LD1 drive circuit 102 and the LD2 drive circuit 103
When a data signal for each pixel (dot) corresponding to image data is received from U101, drive pulses for driving the semiconductor lasers LD1 and LD2 are generated with the same current, and these drive pulses are generated by the semiconductor lasers LD1 and LD2.
Output to

The RAM 105 temporarily stores the number of prints and the print mode. The ROM 104 stores a control program and the like relating to an image forming operation in the image forming unit 50. The CPU 101 generates a data signal for each pixel by performing necessary processing such as shading correction on image data input from an external computer or the like (not shown), and generates the data signal for each pixel.
2 to the driving circuit 103.

While receiving inputs from various sensors, R
A necessary program is read from the OM 104, and the operation in the image forming unit 50 is controlled in a unified manner while taking a timing to execute a smooth printing operation. FIG. 6 is a diagram showing a beam intensity distribution 21a of the beam spot 20a in the sub-scanning direction, and FIG. 7 is a diagram showing a beam intensity distribution 21b of the beam spot 20b.
In both figures, the horizontal axis represents the length in the sub-scanning direction, and the vertical axis represents the beam (exposure) intensity, and the intensity becomes smaller as the center of the dot becomes a peak and moves away from the center.

The beam intensity distribution 21b has a peak of the beam intensity almost 2/3 of that of the beam intensity distribution 21a.
It is twice as small. This is achieved by adjusting the semiconductor laser LD2 to a position shifted from the focal position as described above,
This is because the beam spot 20b was blurred to increase the diameter. By combining the beam intensity distribution 21a and the beam intensity distribution 21b, the beam intensity distribution 21 in the sub-scanning direction of the beam spot 20 can be obtained.

FIG. 8 shows the beam intensity distribution 21 of the beam spot 20 in the sub-scanning direction, and the beam intensity distribution in the sub-scanning direction of a spot image formed when two dots are continuously exposed in the sub-scanning direction. 23 is also shown. The beam intensity distribution 23 has two beam spots 2
The beam intensity distributions 21 and 22 of 0 are combined. Further, the threshold level in the drawing is a threshold value indicating the exposure intensity that can be developed, and a toner image is formed in a portion exceeding the threshold.

FIG. 9 shows a conventional method of exposing one dot with one beam in the conventional method. The beam intensity in the sub-scanning direction of a spot image formed when two dots are continuously exposed in the sub-scanning direction. It is a figure showing distribution 27. The spot diameter of this one beam is the beam spot 20.
Similar to a, the size is approximately 1.5 times the dot pitch.

Comparing the two figures, the intensity difference h between the peak and the valley of the beam intensity distribution 23 is the beam intensity distribution 27.
It can be seen that the intensity difference k is considerably smaller than the intensity difference k. This is because the beam intensity distribution 21 of the beam spot 20 according to the present invention is different from the conventional beam intensity distribution 271.
This is because as the beam intensity decreases, the beam spreads greatly in the sub-scanning direction. That is, the beam spot 20 of the present invention has a smaller peak value than the conventional beam spot, but its diameter is doubled. For this reason, the beam spot 20 exposes not only one dot but also a range that greatly exceeds this. However, since the beam intensity of a portion exposed beyond one dot is lower than the threshold level, a toner image is not formed in that portion even if developed. However, when two dots are continuously exposed, the beam spots 20b having a large diameter overlap each other, so that the beam intensity (peak value) at the central portion of the dot is substantially equal to the peak value of the conventional beam spot. At the same time, the beam intensity at the boundary between the two dots exceeds the threshold level and approaches the peak. As a result, the intensity difference h between the peak and the valley becomes smaller than before.

Next, in the case of the present invention and the prior art, the respective cross-sectional shapes when the beam intensity distribution of a spot image formed when two dots are continuously exposed in the sub-scanning direction are cut at a threshold level. Are shown in FIG. 10 and FIG. As described above, if the beam spot 20 of the present invention is continuously exposed by two dots, the difference h in the beam intensity becomes smaller than in the related art, so that the cross-sectional shape 24 (when the beam intensity distribution is cut at the threshold level) is obtained. In FIG. 10), the depression 241 in the main scanning direction at the boundary between the two dots is smaller than the cross-sectional shape 28 (FIG. 11) formed by the conventional beam spot.

If the concave portion 281 is large as in the conventional spot shape 28, the solid line edge portion connecting the concave portion 281 in the sub-scanning direction tends to be jagged. However, if the depression 241 is small, such as the spot shape 24 obtained by exposing the beam spot 20 according to the present invention, the edge of the solid line connecting the depressions 241 becomes smooth, and this occurs at the edge of the conventional image. Such jaggedness is less likely to occur, and image quality can be improved. In addition, beam spot 20
Are beam spots 20a, 2a having different beam intensities and diameters.
0b is combined, so that the solid line becomes thicker as in the method of increasing the beam intensity and simply increasing the spot diameter to increase the overlapping area between the dots to reduce the dents. It doesn't get worse.

The case where two dots are continuously exposed in the sub-scanning direction has been described above. However, in general, solid lines are rarely formed by only two dots, and three or more dots are connected to form a solid line. It is almost always formed.
Therefore, FIG. 12 shows a beam intensity distribution 25 in the sub-scanning direction when three or more dots are continuously exposed to the beam spot 20, and the intensity difference between the peak and the valley of the beam intensity is compared with the conventional case. .

Referring to the beam intensity distribution 25 in FIG. 12, the intensity difference m between the peak and the valley of the beam intensity is much smaller than the intensity difference k (FIG. 9) in the conventional case described above. You can see that. Further, the intensity difference m is the intensity difference h.
(FIG. 8). This is because the adjacent beam spots 20 overlap each other, so that the beam intensity at the boundary of each dot comes closer to the peak value.

As a result, since the spot-shaped depression is smaller than in the case of two dots, the edge portion of the image can be reproduced more smoothly. Next, FIG. 13 and FIG. 14 compare the electrostatic latent images formed when the continuous 8 dots in the sub-scanning direction are respectively exposed by the beam spot 20 of the present invention and the conventional one-dot one-beam method. View. In FIG. 13, as in FIG. 14, the state where the beam intensity decreases as the distance from the center of the dot decreases is shown by three levels of density change.

From both figures, the depression 261 at the boundary between the dots in the electrostatic latent image 26 is clearly smaller than the depression 291 in the electrostatic latent image 29. Thus, it can be seen that when the electrostatic latent image 26 according to the present invention is developed, the edge portion of the image is reproduced more smoothly than in the related art. Although it has been described above that jagged edges are less likely to occur in a reproduced image when a solid line parallel to the sub-scanning direction is formed, the solid line and the diagonal line parallel to the main scanning direction also have a boundary portion of each dot. The same effect as described above can be obtained because there is no substitute for the reduction in the dent that occurs in. (3) Modified Examples Needless to say, the present invention is not limited to the above-described embodiment, and the following modified examples can be considered.

(3-1) In the above embodiment, the diameter of the beam spot 20b is set to almost twice the diameter of the beam spot 20a, and the peak of the beam intensity is set to almost 2/3 times the beam spot 20a. However, the present invention is not limited to this. The beam spot 20 is obtained by combining the beam spots 20 so that the difference h between the peak and the valley of the beam intensity when the beam spot 20 is continuously exposed is as small as possible. What is necessary is just to set the diameter and peak value of 20a, 20b. In particular, if the diameter of the beam spot 20b is set within a range of 1.65 to 2.25 times the diameter of the beam spot 20a, and the peak value is set within a range of 0.55 to 0.75 times, it is more preferable. Good effects can be obtained.

(3-2) In the above embodiment, the diameter of the beam spot 20b is almost twice as large as that of the beam spot 20a by mounting the semiconductor laser LD2 having the same specifications as the semiconductor laser LD1 at a position shifted from the focal position. However, for example, the beam spot 20b is formed by using a semiconductor laser having a specification different from that of the semiconductor laser LD1, in which the diameter of the emitted laser beam itself is larger than that of the semiconductor laser LD1. You may do so. In this case, the peak of the beam intensity of the beam spot 20b is smaller than that of the beam spot 20a.
The LD2 drive circuit 103 of the control unit 100 is adjusted.

(3-3) As both or one of the semiconductor lasers LD1 and LD2 in the above embodiment, a semiconductor laser capable of changing the beam diameter disclosed in Japanese Patent Application Laid-Open No. 7-89131 may be used. Good. In this case, it is possible to set the optimum relationship between the beam spot diameter and the beam intensity for each change in the pixel density and the type of the reproduced image.

(3-4) In the above embodiment, the laser beams 18a and 18b emitted from the semiconductor lasers LD1 and LD2 are combined so that their optical axes are aligned. However, the optical axes are not perfect but almost coincide with each other. It may be in the state where it was done. In this case, the effect that the difference h (see FIG. 8) between the peak and the valley of the exposure intensity is reduced is obtained to some extent, and the edge portion can be smoothed.

(3-5) In the above embodiment, a full-color laser beam printer has been described. However, the present invention is not limited to this, and a laser beam can be scanned as an image writing means such as a monochromatic laser beam printer or a digital copier. The present invention can be generally applied to an image forming apparatus having an apparatus for performing the above.

[0041]

As described above, according to the present invention, the light beam scanned on the image carrier based on the pixel data is compared with the first light beam and the first light beam. Since it is formed by combining the second light beam having a large spot diameter and a small peak intensity on the image carrier, when exposing continuous pixels, the second light beam having a large diameter is used.
The light beam spots overlap each other in the direction in which the spots are arranged (the direction in which the continuous line extends), so that the exposure intensity at the boundary between pixels can be increased. Accordingly, the electrostatic latent image formed by the continuously exposed beam spots can be formed into a shape in which the boundary portions of the pixels are smoothly connected, and the image quality can be improved.

Further, since the edge portion can be smoothly reproduced with a simple configuration that only combines the first light beam and the second light beam, the shape of the beam spot can be varied for each pixel as in the related art. There is also an effect that simple control is unnecessary and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a printer according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of an exposure scanning unit of the printer.

FIG. 3 is a diagram illustrating a shape of a beam spot for one pixel (dot) when a combined beam emitted from two semiconductor lasers and combined is imaged on a photosensitive drum.

FIG. 4 is a plan view showing a configuration of a light source device.

FIG. 5 is a block diagram illustrating a configuration of a control unit.

FIG. 6 is a diagram showing a beam intensity distribution in a sub-scanning direction of a beam spot formed by a laser beam emitted from one semiconductor laser.

FIG. 7 is a diagram showing a beam intensity distribution in a sub-scanning direction of a beam spot formed by a laser beam emitted from another semiconductor laser.

8 is a diagram showing a beam intensity distribution of the beam spot shown in FIG. 3 in the sub-scanning direction.

FIG. 9 shows a beam intensity distribution in the sub-scanning direction of a spot image formed when two dots are continuously exposed in the sub-scanning direction by a conventional method of exposing one dot with one beam. FIG.

10 is a diagram illustrating a cross-sectional shape when a beam intensity distribution of a spot image formed when two dots are continuously exposed in the sub-scanning direction with the beam spot illustrated in FIG. 3 is cut at a threshold level. .

FIG. 11 shows a conventional method of exposing one dot with one beam, in which a beam intensity distribution of a spot image formed when two dots are continuously exposed in the sub-scanning direction is cut at a threshold level. It is a figure showing the cross-sectional shape at the time.

FIG. 12 shows the beam spot shown in FIG.
FIG. 6 is a diagram illustrating a beam intensity distribution in a sub-scanning direction of a spot image formed when dots or more are continuously exposed.

FIG. 13 shows a beam spot shown in FIG.
FIG. 4 is a diagram illustrating an electrostatic latent image formed when dots are continuously exposed.

FIG. 14 is a diagram showing an electrostatic latent image formed when eight dots are continuously exposed in the sub-scanning direction by the conventional method of exposing one dot with one beam.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Exposure scanning part 11 Light source device 13 Beam splitter 14 Collimator lens 15 Polygon mirror 16 Scanning lens 17 Folding mirror 18a, 18b Laser beam 18c Synthetic beam 20, 20a, 20b Beam spot 21, 21a, 21b, 22, 25, 27 Beam intensity Distribution 24, 28 Cross-sectional shape 26, 29 Electrostatic latent image 31, 32 Holding member 33, 34 Support base 61 Photoconductor drum 100 Control unit 101 CPU 102 LD1 drive circuit 103 LD2 drive circuit 104 ROM 105 RAM 241, 261, 281 , 291 recess LD1, LD2 Semiconductor laser

Claims (1)

[Claims] 1. An image forming apparatus for forming an image by scanning an image carrier with a light beam based on pixel data, wherein the light beam includes a first light beam and the first light beam An image forming apparatus characterized by being formed by combining a second light beam having a larger spot diameter and a smaller peak intensity on an image carrier than a beam.