JP2000168133A - Multi-beam writing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a service person to judge presence or absence of inclined right sources by executing one time of test printing. SOLUTION: When a print start instruction is made at the setting of a test pattern outputting mode, an MPU 20 rotates a polygon mirror at a predetermined rotational speed. The MPU 20 executes an operation for forming a first output pattern consisting of a pixel row wherein pixels are arranged on a photosensitive body in the sub-scanning direction at predetermined intervals by turning-on a predetermined one LD in a plurality of LDs LD1a-LD1d at a predetermined timing in each main scanning of the polygon mirror by using a selector 26. The MPU 20 executes an operation for forming a second output pattern consisting of a pixel row wherein pixels are arranged thereon in the sub- scanning direction in close proximity to one another and away from one another by turning-on a predetermined number of LDs in the plurality of LDs LD1a-LD1d selectively at a predetermined timing different from the above timing in each main scanning of the polygon mirror by using a selector 26. The MPU 20 executes the above both of operations in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam writing apparatus used for an image forming apparatus such as a laser printer, a digital copying machine, and the like.

[0002]

2. Description of the Related Art A multi-beam writing apparatus has a plurality of light sources (for example, laser diodes) at substantially the same position in a main scanning direction and separated by a predetermined distance in a sub-scanning direction which is a rotation direction of a photosensitive member. Beam light (for example, a laser beam) emitted from each of the light sources is periodically deflected by a polygon mirror of a scanner which is an optical scanning means, and the main scanning is performed on the photoconductor surface with a positional difference in the sub-scanning direction on the photoconductor surface. I am trying to do it.

In such a multi-beam writing apparatus, each light source should ideally be arranged perpendicularly (perpendicularly) to the main scanning direction, but is actually arranged with a certain inclination. Sometimes. Therefore, the serviceman must determine whether or not each light source is tilted, and perform a correction operation to eliminate the tilt if the light source is tilted. A key operation instructs the image forming apparatus to start a test print and causes the test print to be performed.

A multi-beam writing apparatus rotates a polygon mirror at a predetermined rotation speed in response to a test print start instruction, and simultaneously turns on all light sources at a predetermined timing for each main scan by the polygon mirror. A test pattern (electrostatic latent image) composed of a pixel row in which pixels are arranged in the sub-scanning direction on the photoconductor surface (precharged surface)
Generate The test pattern is developed by a toner from a developing device of the image forming apparatus to be visualized, transferred to a sheet fed from a sheet feeding unit by a transfer device, and further fixed by a fixing device. The paper is discharged outside the machine.

[0005] A service technician looks at the width (line width) of a test pattern (hereinafter also referred to as an "inclination detection pattern") on a sheet in the main scanning direction to determine whether or not each light source of the multi-beam writing apparatus has an inclination. It is determined, and if it is inclined, a correction operation for eliminating the inclination is performed.

[0006]

By the way, when each light source is tilted and when it is not tilted, as shown in FIGS. 12 and 13, respectively, the test pattern on the paper formed by the test print is changed. Although the width (line width) in the sub-scanning direction is different, the line width also depends on the image forming conditions of the image forming apparatus, and the line width (minimum value) when each light source is not tilted is not fixed. The man can determine the presence or absence of the inclination only by moving each light source. Therefore, it was not possible to determine whether or not each light source position was tilted by performing the test print only once.

The present invention has been made in view of the above points, and has as its object to enable a service person to determine whether or not each light source is tilted by performing test printing only once.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a plurality of light sources and light beams respectively emitted from the respective light sources are periodically deflected by a polygon mirror, and are deflected in a sub-scanning direction on a surface of the photoreceptor to be sub-scanned. In order to achieve the above object, in a multi-beam writing apparatus provided with an optical scanning means for performing main scanning on the surface of the photosensitive member with a positional difference, the following is provided.

According to a first aspect of the present invention, the polygon mirror is rotated at a predetermined rotation speed, and only a specific one of the plurality of light sources is turned on at a predetermined timing for each main scan by the polygon mirror. Thereby, a first process of generating a first output pattern composed of a pixel row in which pixels are arranged at regular intervals on the photoreceptor surface in a sub-scanning direction, and a specific plurality of light sources of the plurality of light sources are formed by a polygon. By selectively turning on the main scanning by the mirror at a predetermined timing different from the above-mentioned predetermined timing, a second output pattern composed of a pixel row in which pixels approach and separate in the sub-scanning direction on the photoreceptor surface is formed. An output pattern generating means for performing the second processing to be generated in parallel is provided.

According to a second aspect of the present invention, in the multi-beam writing apparatus of the first aspect, the output pattern generating means includes a first output pattern and a second output pattern on the photoreceptor surface, each of which is spaced in the main scanning direction. A plurality of columns are placed, and an interval from the first output pattern to a second output pattern adjacent to the upstream side in the main scanning direction and a second output pattern adjacent to the downstream side in the main scanning direction are generated. And means for making the interval different.

According to a third aspect of the present invention, in the multi-beam writing apparatus according to the first aspect, the number of write pixels of the first output pattern and the number of write pixels of the second output pattern generated on the photoreceptor surface by the output pattern generating means. The number is made equal. The invention of claim 4 is claim 1
In the multi-beam writing apparatus, when the output pattern generating means performs the second processing, a plurality of specific light sources to be selectively turned on for each main scan are provided on the photosensitive member surface in one main scan by the polygon mirror. This is a light source that emits a light beam with respect to the leading end position and the trailing end position in the scanning direction.

[0012]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 2 is a perspective view showing a configuration example of a mechanism section of the multi-beam writing device embodying the present invention.

In this multi-beam writing apparatus, reference numeral 1 denotes an LD array in which a plurality of laser diodes (light sources) are housed in one package, and each of the laser diodes (hereinafter abbreviated as "LD") converts an image signal into an image signal. A laser beam (beam light) modulated accordingly is emitted. The plurality of laser beams are collimated by a collimator lens 2, an aperture 8, a scanner (optical scanning means).
The laser beam having a small diameter is shaped into a laser beam having a predetermined shape by the cylindrical lens 3, and the laser beam is applied to the polygon mirror 4.

That is, the plurality of laser beams are:
The collimated lens 2 converts the light beam into a parallel light beam, and then an extra laser beam is cut by an aperture 8 having a slit corresponding to the size of a writing dot (scan density). Each parallel light beam shaped by the aperture 8 is
Each laser beam for writing an image in the main scanning direction is condensed by the cylindrical lens 3 so as to have a predetermined size on the surface (photosensitive surface) of the photosensitive drum 7, and is irradiated on the polygon mirror 4.

Reference numeral 4 denotes a polygon mirror, which is continuously rotating at a predetermined rotation speed, so that the laser beam impinging on the polygon mirror is directed to a mirror 9 where it is reflected (deflected) by the main scanning direction (photosensitive member). It is repeatedly moved and scanned in X) (the axial direction of the drum 7). At this time, the polygon mirror 4
The laser beam reflected by the lens is converted by a pair of Fθ lenses 5 from equiangular motion to uniform motion, and a lens 6
Is corrected by the reflection mirror 9, the angle is changed by the reflection mirror 9, and a spot-shaped image is formed on the surface of the photosensitive drum 7 with a predetermined beam diameter.

Since the LD array 1 has a plurality of LDs, a plurality of LDs having a pitch (position difference) in the sub-scanning direction (rotation direction of the photosensitive drum 7) Y on the surface of the photosensitive drum 7 are provided. Of the laser beam irradiation is drawn.

FIG. 3 is an enlarged perspective view of the LD array 1 of FIG. In the heterodyne junction surface 1A of the LD array 1,
A plurality of LDs are formed. Here, assuming that two LDs are formed for convenience of illustration, the laser beams emitted from the two LDs are B1 and B2 as illustrated. Although the multi-beam writing device of this embodiment includes the LD array 1 having four LDs, two, three, or five or more L
An LD array having D or two or more single LD units may be provided.

In FIG. 2, the laser beam immediately before the main scanning on the photosensitive drum 7 is applied to a laser beam path on the main scanning start point side outside the main scanning writing area (outside the predetermined main scanning width) with respect to the surface of the photosensitive drum 7. Since the laser beam passes through the synchronization detection sensor 11 via the provided synchronization mirror 10, the synchronization detection sensor 11 detects the laser beam and generates a synchronization detection signal. Then, a control unit (not shown) uses the synchronization detection signal from the synchronization detection sensor 11 to control the emission start timing of the laser beam for image recording for each scan.

FIG. 4 shows the relationship between the four laser beams B1, B2, B3, and B4 and the synchronization detection sensor 11 immediately before scanning on the photosensitive drum 7. Note that the synchronization detection sensor 1
Reference numeral 1 denotes a sensor (here, a photodiode) that detects a laser beam outside the main scanning write area on the surface of the photosensitive drum 7 and outputs a laser beam detection signal (beam light detection signal); A synchronization detection signal generator for generating a synchronization detection signal for defining a write start position in the main scanning direction according to the signal.

FIG. 1 is an electric circuit diagram showing an example of a main part of the multi-beam writing device. The MPU 20 is a microcomputer including a central processing unit, a ROM, a RAM, and the like, and controls the entire image forming apparatus including the multi-beam writing device. The MPU 20 functions as an output pattern generating means according to claims 1 to 4 together with a selector 26 and the like described later.

When any one of the four laser beams B1 to B4 hits the photodiode 11a of the synchronous detection sensor 11, the photodiode 11a
Outputs a laser beam detection signal, and the synchronous detection sensor 11
Synchronization detection signal generator (hereinafter referred to as “detection circuit”) 1
1b generates (generates) a synchronization detection signal DP for defining a write start position in the main scanning direction according to the laser beam detection signal.

The main scanning counter 21 is supplied with a write clock WCLK for controlling one dot to be written, and the main scan counter 21 counts this write clock WCLK.

The comparator 22 compares a predetermined value set in advance by the MPU 20 with a count value of the main scanning counter 21 and determines that the count value is a predetermined value (immediately before the laser beam hits the synchronization detection sensor 11, ie, when the laser beam (The timing of passing through the detection sensor 11), the output is changed from low level “L” to high level “H”.
To output a forced lighting signal which is a high level signal.

The switch 23 switches the output terminal of the comparator 22 to one of the input terminals of the OR gates 24a to 24d in response to the SW control signal from the MPU 20, and switches the forced lighting signal from the comparator 22 to the connection destination. Is output to the OR gate.

The OR gate 24a outputs print data from the selector 26 or a forced lighting signal from the changeover switch 23 to an LD driver (LDD) 25a. The OR gate 24b outputs print data from the selector 26 or a forced lighting signal from the changeover switch 23 to the LD driver 25b.

The OR gate 24c outputs print data from the selector 26 or a forced lighting signal from the changeover switch 23 to the LD driver 25c. The OR gate 24d outputs print data from the selector 26 or a forced lighting signal from the changeover switch 23 to the LD driver 25d.

The LD driver 25a includes an OR gate 24a
L in response to print data from
It controls turning on / off of the LD 1a of the D array 1 and generates a corresponding laser beam. The LD driver 25b is
In accordance with the print data or the forcible lighting signal from the R gate 24b, the on / off state of the LD 1b of the LD array 1 is controlled to generate a corresponding laser beam.

The LD driver 25c has an OR gate 24c.
L in response to print data from
It controls turning on / off of the LD 1c of the D array 1 and generates a corresponding laser beam. LD driver 25d is O
The on / off state of the LD 1d of the LD array 1 is controlled in accordance with the print data or the forced lighting signal from the R gate 24d, and a corresponding laser beam is generated.

The selector 26 is provided for each LD 1 of the LD array 1.
An image signal for modulating (lighting or extinguishing) each of a to 1d or test pattern data for selectively modulating the LDs 1a to 1d is selectively input and output as print data. The test pattern data according to the present invention is stored in advance in the RO in the MPU 20.
M or another memory.

When the laser beam immediately before scanning on the photosensitive drum 7 enters the detection area, the synchronization detection sensor 11 detects the laser beam and detects a high-level "H" synchronization detection signal D.
When a laser beam P is generated and the laser beam exits the detection area toward the print area, the synchronization detection signal DP is returned to a low level “L” (the output of the synchronization detection signal DP is stopped).

The main scanning counter 21 and the comparator 22 are reset by the synchronization detection signal DP. Accordingly, the main scanning counter 21 starts counting up from the initial value (0), and the output of the comparator 22 becomes “L”.
(Non-lighting instruction) ”. That is, the output of the forced lighting signal is stopped.

Here, the printing operation in the normal print output mode in the image forming apparatus including the multi-beam writing device will be briefly described. The MPU 20
When a print start is instructed in a state where the normal print output mode is set, a polygon motor (not shown) is rotationally driven to rotate the polygon mirror 4 at a predetermined rotation speed, and the four By modulating and driving each of the LDs 1a to 1d of the LD array 1 in accordance with the image signal, an image (electrostatic latent image) is generated on the surface (precharged surface) of the photosensitive drum 7.

Thereafter, the image formed on the surface of the photosensitive drum 7 is developed with a toner from a developing device (not shown) into a visible image, and is transferred onto a sheet fed from a sheet feeding unit (not shown). After the image is transferred by the apparatus and further fixed by a fixing device (not shown), the sheet on which the image is fixed is discharged outside the apparatus.

By the way, in this multi-beam writing apparatus, the LD array 1 needs to be arranged perpendicular to the main scanning direction, but may actually be arranged with a certain inclination.

When the LD array 1 is not inclined (the LD array 1 is arranged perpendicular to the main scanning direction)
By performing normal printing (image formation), each of the electrostatic latent images formed on the surface of the photosensitive drum 7 by irradiation of the laser beams B1 to B4 from the LDs 1a to 1d of the LD array 1 in the sub-scanning direction. The pixel (dot) row is perpendicular to the main scanning direction, for example, as shown in FIG.

On the other hand, when the LD array 1 is inclined, normal printing is performed to form the surface of the photosensitive drum 7 by irradiating the laser beams B1 to B4 from the LDs 1a to 1d of the LD array 1. Each pixel (dot) row in the sub-scanning direction of the generated electrostatic latent image is inclined in the main scanning direction, for example, as shown in FIG.

Therefore, the serviceman must determine whether or not the LD array 1 is tilted and, if it is tilted, perform a correction operation to eliminate the tilt. Therefore, an image forming apparatus equipped with the multi-beam writing device of this embodiment is required. A key operation on an operation unit (not shown) of the apparatus sets a test pattern output mode according to the present invention and instructs the image forming apparatus to start printing, and causes the image forming apparatus to perform a print (test print) operation in the test pattern output mode. This will be described later in detail.

FIG. 7 is a flow chart showing an example of processing according to the present invention by the MPU 20 of FIG. In the multi-beam writing apparatus, the processing routine of FIG. 7 is started periodically, and it is checked whether or not the test pattern output mode is set. If the test pattern output mode is not set, the normal print output mode is changed to the test pattern output mode. If an output mode has been set, that mode is selected.

At this time, the input of the selector 26 is also switched by the select signal. That is, when the normal print output mode is selected, the selector 26 can input an image signal and output it as print data. When the test pattern output mode is selected, the selector 26 inputs the test pattern data and outputs it as print data.

Next, the printing operation in the test pattern output mode in the image forming apparatus including the multi-beam writing device will be specifically described with reference to FIGS.

FIG. 8 shows an example of the pixel positions (output dot positions) of the test pattern generated on the surface of the photosensitive drum 7 when the printing operation in the test pattern output mode is performed in a state where the LD array 1 is not tilted. FIG. 9 shows an example of pixel positions of a test pattern generated on the surface of the photosensitive drum 7 when a print operation is performed in the test pattern output mode in a state where the LD array 1 is inclined. In the figure, the write pixels are shown shaded.

FIG. 10 is a view for explaining the width (line width) in the sub-scanning direction of the test pattern formed on the paper when the printing operation is performed in the test pattern output mode in a state where the LD array 1 is not tilted. Explanatory drawing, FIG.
FIG. 9 is an explanatory diagram for explaining a width in a sub-scanning direction of a test pattern formed on a sheet when a printing operation in a test pattern output mode is performed in a state where the D array 1 is inclined.

When print start is instructed in a state where the test pattern output mode is set, the MPU 20 rotates a polygon motor (not shown) to rotate the polygon mirror 4 at a predetermined rotation speed, and selects a selector 26 and the like. , The following first processing shown in (1) and the second processing shown in (2) are performed in parallel.

(1) A plurality of LDs 1a to L of LD array 1
One specific LD of D1d (LD1 in the example of FIG. 8)
a, but other LDs may be turned on at a predetermined timing for each main scan by the polygon mirror 4 so that pixels on the surface of the photosensitive drum 7 are arranged at regular intervals in the sub-scan direction. Generate a first output pattern consisting of columns. At this time, test pattern data for lighting the LD 1a at a predetermined timing is output to the LD driver 25a via the selector 26 and the OR gate 24a.

(2) Plural LDs 1a-1 of LD array 1
8, a plurality of specific LDs (LD1a, LD1a in the example of FIG. 8)
1d, but other combinations may be used)
Is selectively lit at a predetermined timing different from the above-mentioned predetermined timing for each main scan by the polygon mirror 4, so that a pixel row in which pixels are arranged on the surface of the photosensitive drum 7 in a sub-scanning direction, approaching and separating from each other. To generate a second output pattern consisting of: At this time, each test pattern data for selectively lighting the LDs 1a and 1d at a predetermined timing is output to the LD driver 25a via the selector 26 and the OR gate 24a.

At this time, in this embodiment, a first output pattern and a second output pattern constituting a test pattern on the surface of the photosensitive drum 7 are generated in a plurality of columns at intervals in the main scanning direction. And an interval a from the first output pattern to a second output pattern adjacent on the upstream side in the main scanning direction and an interval b from a second output pattern adjacent on the downstream side in the main scanning direction. To be different. In the example of FIG. 8, the intervals a and b are set to 4 dots and 7 dots, respectively.

The number of write pixels of the first output pattern and the number of write pixels of the second output pattern generated on the surface of the photosensitive drum 7 are made equal. Further, when performing the second processing shown in (2), a plurality of specific LDs that are selectively turned on for each main scan are provided on the surface of the photosensitive drum 7 in one main scan by the polygon mirror 4. The LDs 1a and 1d emit light beams with respect to the leading end position and the trailing end position in the scanning direction.

Thereafter, a plurality of first output patterns and a plurality of second output patterns, which are test patterns formed on the surface of the photosensitive drum 7, are developed with a toner from a developing device (not shown) into a visible image. The sheet is transferred onto a sheet fed from a sheet feeding unit by a transfer device (not shown), and further fixed by a fixing device (not shown), and then a plurality of first output patterns and a second output pattern are fixed on the sheet. Out of the machine.

Here, if the LD array 1 is not inclined, for example, as shown in FIG. 10, the width of the first output pattern P1 formed on the paper in the main scanning direction and the main width of the second output pattern P2 are changed. The width in the scanning direction becomes the same and becomes the minimum value (the line width becomes the thinnest). However, if the LD array 1 is inclined, the first output formed on the paper as shown in FIG. The width of the second output pattern P2 in the main scanning direction is wider than the width of the pattern P1 in the main scanning direction (the line width is increased).

As described above, according to the multi-beam writing apparatus of this embodiment, the test print as described above
Only once, the serviceman compares the width of the first output pattern formed on the paper in the main scanning direction with the width of the second output pattern in the main scanning direction, thereby obtaining the LD array. The presence or absence of the inclination of 1 can be determined.

When the LD array 1 is tilted,
It is recommended that a service person perform a correction operation to eliminate the inclination of the LD array 1, but instead, a key operation on the operation unit of the image forming apparatus causes a lighting timing for each of the LDs 1 a to 1 d according to the inclination of the LD array 1. May be changed so that the pixel row in the sub-scanning direction of the image formed on the surface of the photosensitive drum 7 is substantially perpendicular (perpendicular) to the main scanning direction.

The embodiment in which the present invention is applied to a multi-beam writing apparatus having a plurality of LDs has been described above. However, the present invention is not limited to this, and the present invention is not limited to this. It can be applied to an apparatus.

[0053]

As described above, according to the multi-beam writing apparatus of the present invention, the polygon mirror is rotated at a predetermined rotation speed, and only one specific light source among a plurality of light sources is used. A first process of generating a first output pattern consisting of a pixel row in which pixels are arranged at regular intervals in the sub-scanning direction on the photoreceptor surface by turning on at a predetermined timing for each main scan by the polygon mirror; By selectively turning on a plurality of specific light sources among the light sources at a predetermined timing different from the above-described predetermined timing for each main scanning by the polygon mirror, pixels approach and separate in the sub-scanning direction on the photoconductor surface. Since the second processing for generating the second output pattern composed of pixel rows arranged in parallel is performed in parallel, the parallel processing (test print) is performed only once, By comparing the width of the first output pattern, which is the test pattern finally formed on the paper, in the main scanning direction with the width of the second output pattern in the main scanning direction, Bisman determines the inclination of each light source. Can be determined.

Further, according to the second aspect of the present invention, a first output pattern and a second output pattern are generated on the photoreceptor surface by a plurality of columns at intervals in the main scanning direction. Since the interval from the output pattern to the second output pattern adjacent on the upstream side in the main scanning direction is different from the interval from the output pattern to the second output pattern adjacent on the downstream side in the main scanning direction, the serviceman needs to When referring to the test pattern finally formed on the paper, the first output pattern and the second output pattern can be easily distinguished, and the presence or absence of the inclination of each light source can be easily determined. .

According to the third aspect of the present invention, the number of write pixels of the first output pattern and the number of write pixels of the second output pattern generated on the photoreceptor surface are made equal to each other, so that finally the paper The density of the first output pattern and the density of the second output pattern formed thereon become the same, and the width of the first output pattern in the sub-scanning direction and the width of the second output pattern in the sub-scanning direction due to the density difference are obtained. Since there is no difference in width, the presence or absence of inclination of each light source can be easily determined.

According to the fourth aspect of the present invention, when performing the above-described second processing, a plurality of specific light sources to be selectively turned on for each main scan are set on the photosensitive member surface in one main scan by the polygon mirror. Since the light sources emit light beams with respect to the foremost position and the rearmost position in the sub-scanning direction, if each light source is inclined, the sub-scanning direction of the second output pattern finally formed on the paper Is the largest, and the presence or absence of inclination of each light source can be easily determined.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an example of a main part of the multi-beam writing device shown in FIG.

FIG. 2 is a perspective view showing a configuration example of a mechanism section of the multi-beam writing apparatus according to one embodiment of the present invention.

FIG. 3 is an enlarged perspective view of the LD array 1 of FIG.

FIG. 4 is a diagram showing a relationship between four laser beams B1, B2, B3, and B4 immediately before scanning on the photosensitive drum 7 in FIG.

FIG. 5 shows a state where the LD array 1 of FIG. 2 is not tilted, and when a printing operation is performed in the normal print mode, the LDs 1a to 1d of the LD array 1 are placed on the surface of the photosensitive drum 7;
FIG. 4 is an explanatory diagram for describing each pixel row in the sub-scanning direction of an electrostatic latent image formed by irradiation of laser beams B1 to B4 from the camera.

FIG. 6 is a diagram showing a state in which the laser beam B1 to B4 from each of the LDs 1a to 1d of the LD array 1 is applied to the surface of the photosensitive drum 7 when a printing operation is performed in the normal print mode with the LD array 1 of FIG. FIG. 4 is an explanatory diagram for describing each pixel row in a sub-scanning direction of an electrostatic latent image formed by irradiation.

FIG. 7 is a flowchart showing an example of a process according to the present invention by the MPU 20 of FIG. 1;

8 is a diagram showing a pixel position of a test pattern (tilt detection pattern) generated on the surface of the photosensitive drum 7 when a print operation is performed in a test pattern output mode in a state where the LD array 1 in FIG. 2 is not tilted. It is explanatory drawing which shows an example.

9 is an explanatory diagram showing an example of pixel positions of a test pattern generated on the surface of the photosensitive drum 7 when a print operation is performed in a test pattern output mode in a state where the LD array 1 in FIG. 2 is inclined. It is.

10 is an explanatory diagram for explaining the width in the sub-scanning direction of a test pattern formed on a sheet when a printing operation is performed in a test pattern output mode in a state where the LD array 1 in FIG. 2 is not tilted. is there.

11 is an explanatory diagram for explaining a width in a sub-scanning direction of a test pattern formed on a sheet when a print operation in a test pattern output mode is performed in a state where the LD array 1 in FIG. 2 is inclined. is there.

FIG. 12 is a view for explaining the width in the sub-scanning direction of a test pattern formed on a sheet when a printing operation is performed in a test pattern output mode in a state where each light source of the conventional multi-beam writing device is not inclined. FIG.

FIG. 13 is a view for explaining the width in the sub-scanning direction of a test pattern formed on a sheet when a printing operation is performed in a test pattern output mode in a state where each light source of the conventional multi-beam writing device is not inclined. FIG.

[Explanation of symbols]

 1: LD (laser diode) array 1a to 1d: LD 4: polygon mirror 7: photosensitive drum 11: synchronization detection sensor 11a: photodiode (sensor) 11b: synchronization detection signal generator (detection circuit) 20: MPU (micro) 21) Main scanning counter 22: Comparator 23: Changeover switch 24a to 24d: OR gate 25a to 25d: LD driver 26: Selector

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C362 AA45 AA47 AA49 BA57 BA69 BA71 CB73 DA03 2H045 AA01 BA23 BA33 CA88 CA92 5C051 AA02 CA07 DB02 DB30 DC05 DE02 DE21 5C072 AA03 BA17 HA02 HA06 HA13 HB08 HB20

Claims (4)

[Claims] A plurality of light sources and light beams respectively emitted from the respective light sources are periodically deflected by a polygon mirror, and are positioned on the photosensitive member surface to be sub-scanned with a positional difference in the sub-scanning direction. A multi-beam writing apparatus comprising: an optical scanning unit that performs main scanning of the polygon mirror. The polygon mirror is rotated at a predetermined rotation speed, and only a specific one of the plurality of light sources is used.
A first process of generating a first output pattern composed of a pixel row in which pixels are arranged at regular intervals in the sub-scanning direction on the photoreceptor surface by turning on the light at a predetermined timing for each of the main scans by the polygon mirror; And selectively turning on a plurality of specific light sources among the plurality of light sources at a predetermined timing different from the predetermined timing for each of the main scans by the polygon mirror. A multi-beam writing apparatus provided with output pattern generating means for performing in parallel with a second process for generating a second output pattern composed of a pixel row in which pixels are arranged close to and away from each other in a scanning direction. . 2. The output pattern generation unit generates the first output pattern and the second output pattern on the photoreceptor surface by a plurality of columns at intervals in the main scanning direction, and generates the first output pattern and the second output pattern. Means for making the interval from the output pattern of the first pattern to the second output pattern adjacent to the upstream side in the main scanning direction different from the interval to the second output pattern adjacent to the downstream side in the main scanning direction. 2. The multi-beam writer according to claim 1, wherein: 3. The method according to claim 1, wherein the number of write pixels of the first output pattern and the number of write pixels of the second output pattern generated on the photoconductor surface by the output pattern generating means are equal. The multi-beam writing device according to claim 1, wherein 4. The multi-beam writing apparatus according to claim 1, wherein the plurality of specific light sources selectively turned on for each of the main scans when the output pattern generating means performs the second processing are: A multi-beam writing device, which is a light source that emits a light beam at a leading end position and a trailing end position in the sub-scanning direction on the photoconductor surface in one main scan by a polygon mirror.