JPH10202948A - Image-forming apparatus and image formation method for image-forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high-quality color images with less color shift at high speed, by controlling a first and a second parts of image information in accordance with a first position signal indicating a rotational position of a rotary polygon mirror and a second position signal indicating a drive position of a carrier body. SOLUTION: A control circuit 50 includes a phase difference between a second position signal detecting a predetermined position of an image carrier body output from a detector 21, and a first position signal detecting a light beam scanned by any one of a plurality of rotary polygonal mirrors output from a detector 30. Based on the phase difference, a feed order of color image information to be modulated for each laser unit 2, 3 is switched for every color image form, so that a plurality of light beams are deflected and scanned with a predetermined time difference on the image carrier body by an optical scanning means from the plurality of the rotary polygonal mirrors with a predetermined angular shift. A color shift amount is limited to a level not larger than one line, and accordingly color images almost without any color shift are superposed to obtain a high-quality color image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus capable of forming a color image and an image forming method of the image forming apparatus.

[0002]

2. Description of the Related Art In recent years, color formation of image forming apparatuses has been rapidly progressing, and image forming apparatuses have been used as various means of expression for users.

[0003] In particular, color page printers have attracted attention because of their quietness, high quality printing quality and high speed printing. Hereinafter, a color laser beam printer which is one of such color page printers will be described as an example.

In the color laser beam printer, in order to perform high-speed printing, a main beam is scanned on a photoconductor at twice the speed of the conventional one by using two-beam laser scanning in addition to one-beam laser scanning. Scanning in the direction
After the first and subsequent odd-numbered scans are performed by the laser and the second and subsequent even-numbered scans are performed by the second laser to form a latent image and develop,
The multi-color image is recorded by transferring the image onto a carrier such as a transfer drum and performing re-transfer collectively on a recording sheet as a recording medium at a predetermined timing.

FIG. 9 is a schematic sectional view illustrating the structure of a conventional color laser beam printer.

In FIG. 1, C is a mechanism of a color laser beam printer. A photosensitive drum 1 is uniformly charged by a charger 4. D denotes an optical unit which is a drawing unit of the printer, and includes a first laser unit 2 having a built-in optical lens, a second laser unit 3, a scanner motor 6, a first polygon mirror 7 rotated by the scanner motor 6, A second polygon mirror 8, a first lens 9,
It is composed of a second lens 10, a first mirror 11, and a second mirror 12, and has a structure that is easily detachable from the main body.

The first image signal S from the first laser unit 2
A first light beam L1 that has been ON / OFF modulated by 110 (hereinafter, referred to as a VDO1 signal) is output. Similarly, the second image signal S111 is output from the second laser unit 3.
(Hereinafter, referred to as VDO2) is output from the second light beam L2 that has been ON / OFF modulated.

The first laser light emitted from the first laser unit 2
After the light beam L1 is scanned by the first polygon mirror 7,
The light is guided to the photosensitive drum 1 via the first lens 9 and the first mirror 11. Similarly, the second light beam L2 emitted from the second laser unit 3 is scanned by the second polygon mirror 8, and then guided to the photosensitive drum 1 via the second lens 10 and the second mirror 12.

Reference numeral 22M denotes a first developing unit which develops a latent image in the first step to form a magenta toner as a first toner image. A second developing unit 22C develops the latent image in the second step to form a cyan toner as a second toner image. A third developing unit 22Y develops the latent image in the third step to form a yellow toner as a third toner image. Reference numeral 22BK denotes a fourth developing unit, which develops the latent image in the fourth step to form a fourth toner image, that is, a black toner.
The developing unit 16 includes the developing units 22C, 22Y, 22M, and 22Bk.

Reference numerals 23 and 24 denote paper cassettes in which recording paper P is stored. The recording paper P is fed one by one by a paper feed roller 25 or a paper feed roller 26 of a paper feed cassette selected by an image processing apparatus described later. Feed paper.

Reference numeral 13 denotes a transfer drum, and a support 14 and
And a film 15. 5 is a cleaner,
The untransferred toner image is scraped off at the end of each transfer step. Reference numeral 17 denotes a fixing device which applies heat to the image transferred to the recording paper P to form a permanent image. Reference numeral 18 denotes a paper discharge tray on which recording paper P on which an image process has been completed is stacked. 19
Is a charger.

Reference numeral 20 denotes a shielding plate, which is used as a reference for print timing on the transfer drum 13. Reference numeral 21 denotes a photo-interrupter. Since the shielding plate 20 on the transfer drum 13 blocks the optical path of the photo-interrupter 21, a reference signal (hereinafter, referred to as T)
(Referred to as an OP signal) is transmitted to an engine control unit and an image generating device, which will be described later, and serves as a print start signal and a reference signal for a print operation.

Next, an image forming sequence will be described.

First, the photosensitive drum 1 is charged to a predetermined polarity and a predetermined voltage by the charger 4, and the VDO1 signal S
The first light beam L1 modulated by 110 and VDO
By scanning and exposing the photosensitive drum 1 with the second light beam L2 modulated by the two signals S111, a first electrostatic latent image is formed. Next, the first electrostatic latent image is developed by the developing device 22M to form a first magenta toner image on the photosensitive drum 1.

On the other hand, a predetermined transfer bias voltage having a polarity opposite to that of the toner is applied to the transfer drum 13, and the first toner image is transferred onto the film 15 on the transfer drum 13.

Next, after a second electrostatic latent image is formed on the photosensitive drum 1 by the first light beam L1 and the second light beam L2, the developing device 22C develops the second electrostatic latent image. A second cyan toner image is formed on the photosensitive drum 1. Then, the second toner image is transferred to the position of the first toner image transferred to the film 15 on the transfer drum 13.

Similarly, third and fourth electrostatic latent images are formed on the photosensitive drum 1, and are respectively developed by the developing units 22Y and 22B.
k, the yellow and black toner images are transferred to the film 15 on the transfer drum 13, the recording paper P is fed at a predetermined timing, and the four color toner images are formed on the film 15 on the transfer drum 13. The toner images of four colors are formed on the recording paper P and are collectively transferred on the recording paper P.

As described above, the VDO1 signal S110 and the VDO2 signal S111 for one page are sequentially output to the first laser unit 2 and the second laser unit 3 for each process.

Thereafter, the recording paper P on which the four color toner images have been transferred is separated from the transfer drum 13. The charger 19 removes the charge accumulated on the recording paper P, and causes air discharge during retransfer separation.

FIGS. 10A and 10B are diagrams for explaining the configuration of the polygon mirrors 7 and 8 shown in FIG. 9, wherein FIG. 10A corresponds to a state viewed from the top, and FIG. 10B corresponds to a state viewed from the side. I do.

As shown in this figure, the first polygon mirror 7
And the second polygon mirror 8 are positioned on the rotation axis of the motor 6, and are finely adjusted so that the reflection surfaces of the respective polygon mirrors coincide with each other, and the first light beam L1 and the second light beam L2 are exposed in substantially the same phase. Scanning on the drum 1.

FIG. 11 is a perspective view showing an optical scanning optical path in the optical unit D shown in FIG. However, the first mirror 11 and the second mirror 12 shown in FIG. 9 are omitted to make FIG. 11 easier to see. Both mirrors are used for changing the optical path, and do not significantly change the description of the conventional example.

As shown in FIG. 1, a first light beam L1 sent from a first laser unit 2 passes through a first lens 9 by a first polygon mirror 7 which is rotated at a constant speed by a motor 6, and is on the photosensitive drum 1. In the main scanning direction (the axial direction of the photosensitive drum 1).

Similarly, the second light beam L 2 sent from the second laser unit 3 is rotated by the motor 6 at a constant speed.
The polygon mirror 8 scans the photosensitive drum 1 in the main scanning direction (the axial direction of the photosensitive drum 1) through the second lens 10. Here, a first photodetector 30 composed of a pin photodiode or the like is located near the main scanning start position of the first light beam L1, and the VDO1 signals S110 and VDO are provided.
A synchronizing signal (hereinafter referred to as a BD1 signal) S10 in the main scanning direction common to the two signals S111 is generated.

FIG. 12 is a block diagram for explaining a control configuration of the main scanning system of the optical scanning system shown in FIG.
The same components as those described above are denoted by the same reference numerals.

In the figure, reference numeral 52 denotes a reference oscillator, which sends a reference clock S12 to a frequency divider 53. Frequency divider 53
Sends a reference signal S13 obtained by dividing the reference clock S12 to a predetermined integer ratio to the motor control circuit 54. The motor control circuit 54 sends the drive signal S14 to the motor 6, and at the same time, controls the feedback signal S15 from the motor 6 and the input reference signal S13 so that the phase difference becomes a predetermined value, and the motor 6 is maintained at a constant speed. Control.

Accordingly, the two first polygon mirrors 7 and the second polygon mirror 8 fixed on the rotation axis of the motor 6 are also rotated at a constant speed, are reflected by both mirrors, and scan the photosensitive drum 1. The two first light beams L1 and second light beam L2 are scanned at a constant period.

Next, each time the shield plate 20 on the transfer drum 13 which rotates at a constant speed by a driving means (not shown) makes one rotation, a photo interrupter (detector) 21 outputs a reference signal (hereinafter referred to as TOP) at the leading end of the image at a constant period. S20) is sent to the image generator 61. Similarly, the BD1 signal S10 output from the first photodetector 30 is also sent to the image generator 61.

The image generating device 61 sends the image signals VDO1 signal S110 and VDO2 signal S111 to the first laser 2 and the second laser 3, respectively, in synchronization with the BD1 signal S10 according to the TOP signal S20.

FIG. 13 shows the TOP signal S2 shown in FIG.
0, BD1 signal S10, VDO1 signal S110 and V
6 is a timing chart illustrating a relationship of a DO2 signal S111. Here, steps only when forming the latent images of the first color and the second color are shown.

In the figure, T1 is the cycle of the transfer drum 13 rotating at a constant speed, T2 is the cycle of the BD1 signal S10 output from the first photodetector 30, and t1 is the TOP signal S2
0 and the phase difference between the BD1 signal S10 and t2 are the TOP signal S2
5 shows a phase difference between 0 and the VDO1 signal S110.

Since the VDO1 signal S110 is an image signal of an odd line, V1, V3,...
Since the VDO2 signal S111 is an image signal of an even line, V2, V4,... V (2n)
Similarly, for the second color, V1 ', V1
2 ′,... V (2n + 1) ′ are represented by VDO2 signal S
Since 111 is an image signal of an even line, V2 ', V
.., V (2n) '.

As can be seen from the figure, the phase difference between the TOP signal S20 and the BD1 signal S10 at the time of forming the first color latent image is t1, but the BD1 signal S1 at the time of forming the second color latent image.
This indicates that when 0 precedes the TOP signal S20, it differs from t1 '.

The reason for this is that the load of the transfer drum 13 and the photosensitive drum 1 on the driving means (not shown) during the printing process is not constant, so that the rotation fluctuates and the period T1 fluctuates.

As described above, t2 and t3 corresponding to the image writing position from the leading edge of each color are also different, so that the final toner image on the transfer drum 13 corresponding to each color is (t3-t).
A color shift corresponding to 2) is generated.

[0036]

FIG. 14 is a view for explaining the color misregistration state of the toner image on the transfer drum 13 shown in FIG. 9. The maximum color misregistration (t3-t2) is different from that of the first color. The toner image is transferred onto the transfer drum 13 with the second color shifted by one line.

In the drawing, d is a color shift within an allowable range which occurs when the two polygon mirrors 7 and 8 are attached to the motor 6. W indicates the line width of one line.

As described above, when the toner images of the first color and the second color are superimposed, the one line width W on the right side of FIG. The pixel line V1 and the pixel line V1 ', which must be formed, do not overlap at all, and a monochromatic toner image is generated, and a color shift of one line occurs in a final print image, resulting in deterioration of print quality. There was a point.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide an image forming apparatus for forming an image by scanning a plurality of light beams on an image carrier. An object of the present invention is to provide an image forming apparatus and an image forming method for the image forming apparatus, which can obtain a high-quality color image at a low speed while obtaining a small high-quality color image.

[0040]

According to a first aspect of the present invention, there is provided a first rotating polygon mirror for scanning an image carrier with a light beam based on a first portion of image information; A second rotating polygon mirror for scanning the image carrier with a light beam based on the two portions, a first driving unit for rotating the first rotating polygon mirror and the second rotating polygon mirror, and the image carrier Driving means, a first generating means for generating a first position signal indicating a rotational position of the first rotating polygon mirror or the second rotating polygon mirror, and a driving position of the image carrier. Second generating means for generating a second position signal as shown in the table, and controlling the first part of the image information and the second part of the image information according to the first position signal and the second position signal. And control means for performing the operation.

According to a second aspect of the present invention, there is provided a third rotating polygon mirror for scanning the image carrier with a light beam based on the third portion of the image information.

According to a third aspect of the present invention, the control means sets one of the first portion and the second portion to an odd line of the image information and the other to an even line.

According to a fourth aspect of the present invention, a plurality of light emitting means for emitting a plurality of light beams modulated based on predetermined color image information, and an image carrier having the plurality of light beams with a predetermined time difference. An optical scanning means in which a plurality of rotating polygon mirrors are stacked along a rotation axis direction with a predetermined angle shift so as to deflect and scan upward, and a first driving means for rotating the optical scanning means at a predetermined speed. Driving means, first detecting means for detecting a light beam scanned by any one of the plurality of rotating polygon mirrors and outputting a first position signal, and rotating the image carrier at a predetermined speed A second drive unit, a second detection unit that detects a predetermined position of the image carrier that is rotationally driven by the second drive unit, and outputs a second position signal, and the second detection unit The second position signal output from And deriving means for deriving a phase difference between the first position signal outputted from the serial first detecting means,
Control means for switching the data transmission order of color image information for modulating each light emitting means based on the phase difference derived by the deriving means for each color image formation.

According to a fifth aspect of the present invention, the control means includes an even image line data and an odd image line data of color image information for modulating each light emitting means based on the phase difference derived by the deriving means. The transmission order with the data is switched and controlled for each color image formation.

According to a sixth aspect of the present invention, there is provided a developing unit for developing a latent image formed by a plurality of light beams scanned on the image carrier with a plurality of color developers in a plane-sequential manner. is there.

According to a seventh aspect of the present invention, a plurality of light emitting means for emitting a plurality of light beams modulated based on predetermined color image information, and an image carrier having the plurality of light beams with a predetermined time difference. An optical scanning means in which a plurality of rotating polygon mirrors are stacked along a rotation axis direction with a predetermined angle shift so as to deflect and scan upward, and a first driving means for rotating the optical scanning means at a predetermined speed. An image forming method for an image forming apparatus, comprising: a driving unit; and a second driving unit configured to rotationally drive the image carrier at a predetermined speed, wherein the light beam is scanned by any one of the plurality of rotating polygon mirrors. And outputting a first position signal and detecting a predetermined position of the image carrier that is rotationally driven by the second driving means, and outputting a second position signal. 2 and the second detecting step. A deriving step of deriving a phase difference between the position signal and the first position signal, and a data transmission order of color image information to be modulated by each light emitting means based on the phase difference derived by the deriving means. And a switching step of switching for each formation.

According to an eighth aspect of the present invention, there are provided a plurality of light emitting means for emitting a plurality of light beams modulated based on predetermined color image information, and a plurality of optical means for deflecting and scanning each light beam on an image carrier. A scanning unit, a plurality of first driving units for rotating each optical scanning unit at a predetermined speed, and a plurality of first driving units so that a phase difference between light beams scanned by each optical scanning unit is の of a main scanning period. Scanning control means for controlling the driving of the first driving means, and a first means for detecting a light beam scanned by one of the plurality of rotary polygon mirrors and outputting a first position signal.
Detecting means, a second driving means for driving the image carrier to rotate at a predetermined speed, and a second position signal detecting the predetermined position of the image carrier which is rotationally driven by the second driving means. And a phase difference between the second position signal output from the second detection unit and the first position signal output from the first detection unit. A deriving unit; and a control unit that controls switching of a data transmission order of color image information to be modulated for each light emitting unit based on the phase difference derived by the deriving unit for each color image formation.

[0048]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIG. 1 is a perspective view of a main part for explaining an optical scanning optical path of an image forming apparatus according to a first embodiment of the present invention, and portions having the same functions as those in FIG. , The description is omitted.

In the figure, the first polygon mirror 7 and the second
As shown in the figure, the polygon mirror 8 is laminated along the rotation axis direction with a predetermined angle shift so that the plurality of light beams L1 and L2 are deflected and scanned on the image carrier with a predetermined time difference. It is arranged in the state where it was done. Reference numeral 30 denotes a first photodetector which detects a first light beam L1 and outputs a first light beam L1.
A D1 signal S10 is generated. A second photodetector 31 detects a second light beam L2 and generates a BD2 signal S20 described later.

FIG. 2 is a diagram for explaining the relative arrangement of the first polygon mirror 7, the second polygon mirror 8, and the motor 6 shown in FIG.
Corresponds to a state in which the second polygon mirror 8 is viewed from above,
(B) corresponds to a state where the first polygon mirror 7, the second polygon mirror 8, and the motor 6 are viewed from the side.

The image forming apparatus according to the present embodiment has a first
The polygon mirror 7 and the second polygon mirror 8 are located on the rotation axis of the motor 6, and the reflection surfaces of the respective polygon mirrors are mounted so as to be shifted from each other. The amount of displacement of the reflecting surface is finely adjusted, and the arrangement is such that the phase difference between the first light beam L1 and the second light beam L2 is の of the main scanning period as shown in FIG.

FIG. 3 is a block diagram for explaining the configuration of the main scanning control of the optical unit D of the image forming apparatus according to the present invention. The same components as those in FIG. 12 are denoted by the same reference numerals.

In the figure, 50 is a control circuit, and TO
BD1 signal S10 or B based on P signal S20
Based on the phase difference of the D2 signal S11, a switching signal S30 of the switching means 51 described later is output to the switching means 51.

Reference numeral 61 denotes an image generating device which switches an odd-numbered line image signal S110 'in synchronization with a main scanning synchronizing signal S10' inputted from a switching means 51 described later.
Output to Similarly, the image signal S of the even-numbered line is synchronized with the main scanning synchronization signal S11 'input from the switching means 51.
111 'is output to the switching means 51. Reference numeral 51 denotes signal switching means for performing the following two types of switching.

At the time of the first switching control, the BD1 signal S
10 is output to the image generator 61 as the S10 'signal and the BD2 signal S11 is output as the S11' signal. As a result, the image signal S110 'corresponding to the odd-numbered line is changed to the VDO1 signal S110'.
110, the image signal S111 ′ corresponding to the even line is output to the first laser unit 2,
The signal is output to the second laser unit 3 as two signals S111.

On the other hand, during the second switching control, BD1
The signal S10 is an S11 'signal, and the BD2 signal S11 is an S1 signal.
It is output to the image generator 61 as a 0 'signal. As a result, the image signal S110 'corresponding to the odd-numbered line is
The signal is output to the second laser unit 3 as two signals S111, and the image signal S111 ′ corresponding to the even line is output to the first laser unit 2 as the VDO1 signal S110.

The control circuit 50 controls the TOP signal S20
The main scanning signal that is input first following the BD1 signal S1
When the value is 0, the first switching control is performed. When the main scanning signal input first after the TOP signal S20 is the BD2 signal S11, the second switching is performed.

FIG. 4 is a timing chart for explaining the control operation of the control circuit 50 and the switching means 51 shown in FIG. 3. In FIG. 4, the same elements as those in FIG. The example shows a case where the first switching is performed in the first color latent image format, and a case where the second switching is performed in the formation of the second color latent image.

First, in forming the latent image of the first color, TO
B generated first in P signal S20 (after t1 in the figure)
The D1 signal S10 is used as the S10 'signal as the image generator 61.
Is output to At the same time, the odd line image signal S11
0 ′ is output to the first laser unit 2 as the VDO1 signal S110. After t4 (after T2 / 2), the image signal S111 'of the even line is output to the second laser unit 3 as the VDO2 signal S111.

Next, in the formation of the latent image of the second color, the switching means 51 is switched so that the BD2 signal S11 generated first (after the timing t5 in the figure) in the TOP signal S20 is changed to the BD1 signal as the S10 'signal. The signal S10 is S1
It is output to the image generator 61 as a 1 'signal.

At the same time, the odd-numbered line image signal S110 'is output to the second laser unit 3 as the VDO2 signal S111. After t3, the image signal S11 of the even-numbered line
1 'is output to the first laser unit 2 as the VDO1 signal S110.

That is, an image signal synchronized with a main scanning signal generated after the TOP signal first is an odd line, and the other is an even line. At this time, the final toner image on the transfer drum 13 at t2 and t5 corresponding to the image writing position from the leading end of the paper of each color is (t5-t).
A color shift corresponding to 2) is generated, but this can be suppressed to ± 1/2 line at the maximum.

FIG. 5 is a diagram for explaining the color misregistration state of the toner image on the transfer drum 13 shown in FIG. 1. According to the present embodiment, the maximum color misregistration is (t5−t2). 1
In the superimposition of the toner images of the first color and the second color, the toner image is transferred onto the transfer drum 13 with a １ ／ line shift between the first color and the second color.

As described above, the color shift when the first color toner image and the second color toner image are superimposed is only a half line width at the maximum.

Hereinafter, the relationship between the respective means in the present embodiment will be described with reference to FIG.

In the present embodiment, a plurality of light emitting means (laser units (lasers) 2 and 3) for emitting a plurality of light beams modulated based on predetermined color image information, and the plurality of light beams Optical scanning means (polygon mirrors 7 and 8 shown in FIG. 1) in which a plurality of rotating polygon mirrors are stacked along a rotation axis direction with a predetermined angle shift so as to deflect and scan the image carrier with a time difference. A first driving means (scanner motor 6) for driving the optical scanning means to rotate at a predetermined speed; and a first position signal detecting a light beam scanned by one of the plurality of rotating polygon mirrors. Detection means (detector 30 or detector 31) for outputting
A second driving means (a drum motor, not shown) for driving the image carrier to rotate at a predetermined speed; and detecting a predetermined position of the image carrier which is rotationally driven by the second driving means. Detecting means (detector 21) for outputting the position signal of the second position signal, the second position signal output from the second detecting means, and the first position output from the first detecting means. Deriving means for deriving a phase difference from the signal (the control circuit 50 counts a predetermined clock and performs deriving processing);
Control means (control circuit 5) for switching and controlling the data transmission order of color image information for modulating each light emitting means based on the phase difference derived by the deriving means for each color image formation;
0 controls the switching of the switching means 51), and the control circuit 50 controls the position of the second position signal output from the detector 21 and the position of the first position signal output from the detector 30. A phase difference is derived, and based on the derived phase difference, the data transmission order of the color image information to be modulated in each of the laser units 2 and 3 is switched for each color image formation, and a plurality of colors are provided with a predetermined angle shift. Since a plurality of light beams are deflected and scanned on the image carrier with a predetermined time difference on the image carrier by an optical scanning means in which a rotating polygon mirror is stacked along the rotation axis direction, the color shift of each color image superimposed in a plane sequence. The amount can be suppressed to a level of one line or less, and a high-quality color image can be obtained by superimposing color images having substantially no color shift.

The control circuit 50 controls the switching of the transmission order of the even-numbered image line data and the odd-numbered image line data of the color image information for modulating each light emitting means based on the derived phase difference for each color image formation. Therefore, the positional deviation between the odd-numbered image data sequence and the several-image line data sequence that are sequentially superimposed can be significantly reduced as compared with the related art.

Further, a developing unit (4 equivalent to the developing unit 16 shown in FIG. 9) for developing a latent image formed by a plurality of light beams scanned on the image carrier with a plurality of color developers in a face-sequential manner. Since the image is developed by color (yellow (Y), magenta (M), cyan (C), and black (K)), a color image having substantially no color shift can be formed. it can.

[Second Embodiment] In the first embodiment, the second photodetector 31 for detecting the second light beam L2 is used.
Has been described, and the case where the BD2 signal S11 is generated has been described. However, the configuration may be such that the BD2 signal is generated based on the output signal BD1 signal of the first photodetector 30.

FIG. 6 is a block diagram for explaining the control configuration of the main scanning system of the image forming apparatus according to the second embodiment of the present invention. The same components as those in FIG. 3 are denoted by the same reference numerals. .

In the figure, reference numeral 70 denotes a delay circuit which delays the BD1 signal and delays the signal BD by 1/2 of the main scanning period T2.
Generate two signals.

As a result, the color shift equivalent to that of the first embodiment can be reduced to 1/2 line or less.

[Third Embodiment] In the first and second embodiments, the case has been described in which the optical units for simultaneously rotating and driving two polygon mirrors by one scanner motor are provided. Accordingly, the present invention can be applied to an image forming apparatus in which polygon mirrors are respectively driven. Hereinafter, the embodiment will be described.

FIG. 7 is a perspective view of an essential part for explaining an optical scanning optical path of an image forming apparatus according to a third embodiment of the present invention.
The same components as those in FIG. 1 are denoted by the same reference numerals.

The difference from the first embodiment is that the first polygon mirror 40 and the second polygon mirror 41 are independently rotated by the first motor 42 and the second motor 43, respectively. The rotation of each motor is controlled so that the phase difference between the first light beam L1 and the second light beam L2 reflected by each polygon mirror is の of the main scanning cycle.

FIG. 8 is a block diagram for explaining the main scanning control configuration of the optical unit of the image forming apparatus shown in FIG. 7, and the same components as those in FIGS. 1 and 3 are denoted by the same reference numerals. .

Hereinafter, the relationship between the respective means of the present embodiment will be described with reference to FIG.

In this embodiment, a plurality of light emitting means (laser units 2 and 3) for emitting a plurality of light beams modulated based on predetermined color image information, and each light beam is deflected onto an image carrier. A plurality of optical scanning means (polygon mirrors 40 and 41) for scanning by scanning, and a plurality of first driving means (scanner motor 4) for rotating each optical scanning means at a predetermined speed.
Scanning control means (motor control circuit 5) for controlling the driving of each first driving means so that the phase difference of each light beam scanned by each optical scanning means is の of the main scanning period.
4, 57, a delay circuit 55) and a light beam scanned by any one of the plurality of rotary polygon mirrors, and
Detecting means (detectors 30, 3) for outputting position signals
1) and a second operation of rotating the image carrier at a predetermined speed.
Driving means (a drum motor not shown) and a second detecting means (detector 21) for detecting a predetermined position of the image carrier rotated and driven by the second driving means and outputting a second position signal. ) And a deriving means (the control circuit 50 derives a phase difference between the second position signal output from the second detecting means and the first position signal output from the first detecting means). The data transmission order of the color image information to be modulated by each light emitting means based on the phase difference derived by the deriving means is derived for each color image formation. Control means (control circuit 50 controls an RO (not shown)
The control circuit 50 executes the control program stored in the M and the like to perform switching control), and the control circuit 50 outputs the second position signal output from the detector 21 and the first position signal output from the detector 30. A phase difference from the position signal is derived, and based on the derived phase difference, the data transmission order of the color image information to be modulated by each of the laser units 2 and 3 is switched for each color image formation, and the motor control circuit 54, 57, each polygon mirror 4 driven with a predetermined phase difference by the delay circuit 55
Since a plurality of light beams are deflected and scanned on the image carrier with a predetermined time difference by 0 and 41, the amount of color misregistration of each color image superimposed in a plane-sequential manner is suppressed to a level of one line or less, and substantially color A high-quality color image can be obtained by superimposing color images without deviation.

The difference between the present embodiment and the first embodiment is that a second motor control circuit 57 for rotating the second motor 43 at a constant speed, a second frequency divider 56 and a delay The point is that the circuit 55 is added.

In the figure, reference numeral 52 denotes a reference oscillator common to the first motor 6 and which outputs a reference clock S12 to the first frequency divider 5
3 and the second frequency divider 56. The second frequency divider 56 generates a reference signal S obtained by dividing the reference clock S12 by a predetermined integer ratio.
16 to the second motor control circuit 57. The second motor control circuit 57 sends the drive signal S17 to the second motor 43, and at the same time, controls the output signal S18 from the delay circuit 55 and the input reference signal S16 so that the phase difference becomes a predetermined value. Control is performed to keep the motor 43 at a constant speed.

Here, the delay circuit 55 delays the input feedback signal S15 of the first motor 6 by a predetermined phase and outputs an output signal S18 to the second motor control circuit 57. Delay circuit 55
The amount of phase delay caused by the polygon mirror 4 of the first motor 6
It is set to be の of the main scanning period T2 of 0.

Accordingly, the first light beam L1 reflected by the first polygon mirror 40 and scanned on the photosensitive drum 1 and the second light beam L2 reflected by the second polygon mirror 41 and scanned on the photosensitive drum 1 Are scanned at a constant period T2 while maintaining a phase difference of T2 / 2. The other control is the same as that of the first embodiment, and the description is omitted.

It is needless to say that the same result can be obtained by combining the third embodiment and the second embodiment.

In the above embodiment, the case where two polygon mirrors are used has been described. However, the present invention is not limited to this, and may be applied to an apparatus having three or four or more polygon mirrors. . In that case, the main scanning line in the image is divided into three or more, and each polygon mirror is assigned.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus. In this case, by reading a storage medium storing a program represented by software for achieving the present invention into the system or the apparatus, the system or the apparatus can enjoy the effects of the present invention. .

Further, by downloading and reading out a program represented by software for achieving the present invention from a database on a network by a communication program, the system or apparatus can be
It is possible to enjoy the effects of the present invention.

As described above, the storage medium storing the program codes of the software for realizing the functions of the above-described embodiments is supplied to the system or the apparatus, and the computer (or CPU or MP) of the system or the apparatus is provided.
It goes without saying that the object of the present invention is also achieved when U) reads and executes the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the novel function of the present invention, and the storage medium storing the program code constitutes the present invention.

Examples of a storage medium for supplying the program code include a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, and C
DR, magnetic tape, nonvolatile memory card, RO
M, EEPROM and the like can be used.

The computer executes the readout program code, not only to realize the functions of the above-described embodiment, but also to execute an OS (Operating System) running on the computer based on the instruction of the program code. ) And the like perform part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, The CPU provided in the function expansion board or function expansion unit performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

As a specific example, a plurality of light emitting means (laser units 2 and 3) for emitting a plurality of light beams modulated based on predetermined color image information, and the plurality of light beams An optical scanning means (polygon mirrors 7, 8) in which a plurality of rotating polygon mirrors are stacked along a rotation axis direction with a predetermined angle shift so as to deflect and scan the image carrier with a time difference; First driving means (scanner motor 6) for driving the scanning means to rotate at a predetermined speed
And a second driving means for driving the image carrier to rotate at a predetermined speed, comprising detecting a light beam scanned by one of the plurality of rotating polygon mirrors. To output the first position signal
And a second detecting step of detecting a predetermined position of the image carrier that is rotationally driven by the second driving unit and outputting a second position signal (a step of following a procedure not shown in the flowchart). Step according to a procedure of a flowchart (not shown)), the second position signal and the first
Deriving step for deriving a phase difference from the position signal of the color image data (step according to a procedure of a flowchart not shown), and a data transmission order of color image information to be modulated by each light emitting means based on the phase difference derived by the deriving means. The CPU (not shown) in the control circuit 50 executes a control program stored in a memory resource such as a ROM, and performs a switching process (step according to a procedure of a flowchart not shown) for switching the image data for each color image formation. The color misregistration amount of each color image can be suppressed to a level of one line or less, and a color image with substantially no color misregistration can be superimposed to obtain a high quality color image.

[0093]

As described above, the first embodiment according to the present invention is described.
According to the third aspect, the first rotating polygon mirror that scans the image carrier with the light beam based on the first portion of the image information, and the image is formed by the light beam based on the second portion of the image information. A second rotating polygon mirror for scanning on the carrier, a first driving unit for driving the first rotating polygon mirror and the second rotating polygon mirror to rotate, a second driving unit for driving the image carrier, First generating means for generating a first position signal indicating the rotational position of the first or second rotating polygon mirror, and second generating means for generating a second position signal indicating the driving position of the image carrier. (2) and control means for controlling the first part of the image information and the second part of the image information according to the first position signal and the second position signal. High-quality color images with low image quality High speed it is possible to obtain a color image.

According to the fourth invention, the deriving means is provided with the second
Derives a phase difference between the second position signal output from the detecting means and the first position signal output from the first detecting means, and the control means The data transmission order of the color image information to be modulated by each light emitting means is switched for each color image formation, and an image is formed by an optical scanning means in which a plurality of rotating polygon mirrors are stacked along the rotation axis direction with a predetermined angle shift. Since a plurality of light beams are deflected and scanned on the image carrier with a predetermined time difference on the image carrier, the amount of color misregistration of each color image superimposed in a plane-sequential manner is suppressed to a level of one line or less, and a color image with substantially no color misregistration is obtained. And a high-quality color image can be obtained.

[0095] According to the fifth aspect of the present invention, the control means controls the even-numbered image line data and the odd-numbered image line data of the color image information for modulating each light emitting means based on the phase difference derived by the deriving means. Are controlled for each color image formation, so that the positional deviation between the sequentially superimposed odd-numbered image data row and even-numbered image line data row can be remarkably suppressed as compared with the related art.

According to the sixth aspect, a latent image formed by a plurality of light beams scanned on the image carrier is developed by a developing unit which develops a plurality of color developers in a plane-sequential manner. A color image without color shift can be formed.

According to the seventh aspect, a deriving step of deriving a phase difference between the second position signal and the first position signal, and each light emission based on the phase difference derived by the deriving means. Since the data transmission order of the color image information to be modulated is switched for each color image formation, the color misregistration amount of each color image superimposed in a sequential manner is suppressed to a level of one line or less,
High-quality color images can be obtained by superimposing color images having substantially no color shift.

According to the eighth aspect, the deriving means includes the second
Derives a phase difference between the second position signal output from the detecting means and the first position signal output from the first detecting means, and the control means The data transmission order of the color image information to be modulated by each light emitting means is switched for each color image formation, and a plurality of light beams are emitted on the image carrier by each optical scanning means driven with a predetermined phase difference by the scanning control means. Since deflection scanning is performed on the image carrier with a predetermined time difference, the amount of color misregistration of each color image superimposed in a plane-sequential manner is suppressed to a level of one line or less, and color images with substantially no color misregistration are superimposed to form a high-quality color image. Obtainable.

Accordingly, there is an effect that a color shift of a color image formed in a frame-sequential manner with a simple structure can be reduced and a high-quality color image can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of an essential part for explaining an optical scanning optical path of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a relative arrangement configuration of a first polygon mirror, a second polygon mirror, and a motor illustrated in FIG. 1;

FIG. 3 is a block diagram illustrating a configuration of main scanning control of an optical unit of the image forming apparatus according to the present invention.

FIG. 4 is a timing chart for explaining a control operation of a control circuit and a switching unit shown in FIG. 3;

FIG. 5 is a diagram illustrating a color misregistration state of the toner image on the transfer drum illustrated in FIG. 1;

FIG. 6 is a block diagram illustrating a control configuration of a main scanning system of an image forming apparatus according to a second exemplary embodiment of the present invention.

FIG. 7 is a main part perspective view illustrating an optical scanning optical path of an image forming apparatus according to a third embodiment of the present invention.

8 is a block diagram illustrating a main scanning control configuration of an optical unit of the image forming apparatus illustrated in FIG.

FIG. 9 is a schematic sectional view illustrating the configuration of a conventional color laser beam printer.

FIG. 10 is a diagram illustrating a configuration of a polygon mirror illustrated in FIG. 9;

11 is a perspective view showing an optical scanning optical path in the optical unit shown in FIG.

FIG. 12 is a block diagram illustrating a control configuration of a main scanning system of the optical scanning system illustrated in FIG.

FIG. 13 shows a TOP signal, a BD1 signal, and a V signal shown in FIG.
5 is a timing chart illustrating a relationship between a DO1 signal and a VDO2 signal.

14 is a diagram illustrating a color misregistration state of the toner image on the transfer drum illustrated in FIG.

[Explanation of symbols]

 2 Laser 3 Laser 6 Motor 21 Detector 30 Detector 31 Detector 50 Control Circuit 52 Reference Oscillator 53 Divider 54 Motor Control Circuit 51 Switching Means 61 Image Generator

Claims (8)

[Claims] A first rotating polygon mirror for scanning the image carrier with a light beam based on a first part of the image information; and a light beam based on a second part of the image information on the image carrier. A second rotating polygon mirror for scanning; a first driving unit for rotating the first rotating polygon mirror and the second rotating polygon mirror; a second driving unit for driving the image carrier; and the first rotation. First generating means for generating a first position signal indicating the rotational position of the polygon mirror or the second rotary polygon mirror, and second generating means for generating a second position signal indicating the driving position of the image carrier A first part of the image information and a second part of the image information according to the first position signal and the second position signal.
An image forming apparatus comprising: a control unit that controls a part. 2. The image forming apparatus according to claim 1, further comprising a third polygon mirror for scanning the image carrier with a light beam based on a third portion of the image information. 3. The image forming apparatus according to claim 1, wherein the control unit sets one of the first part and the second part to an odd line of the image information and the other to an even line. . 4. A plurality of light emitting means for emitting a plurality of light beams modulated on the basis of predetermined color image information, and the plurality of light beams are deflected on an image carrier with a predetermined time difference for scanning. An optical scanning unit in which a plurality of rotary polygon mirrors are stacked along a rotation axis direction with a predetermined angular deviation, a first driving unit that rotates the optical scanning unit at a predetermined speed, and the plurality of rotations. A first detection unit that detects a light beam scanned by one of the polygon mirrors and outputs a first position signal; a second driving unit that rotates the image carrier at a predetermined speed; A second detection unit that detects a predetermined position of the image carrier that is rotationally driven by a second driving unit and outputs a second position signal; and the second detection unit that is output from the second detection unit. From the position signal and the first detection means Deriving means for deriving a phase difference from the output first position signal; and a data transmission order of color image information for modulating each light emitting means based on the phase difference derived by the deriving means. An image forming apparatus, comprising: control means for performing switching control for each formation. 5. The control unit according to claim 1, wherein the order of transmitting even image line data and odd image line data of color image information for modulating each light emitting unit based on the phase difference derived by the deriving unit is determined for each color image. 5. The image forming apparatus according to claim 4, wherein switching control is performed for each formation. 6. The image forming apparatus according to claim 4, further comprising a developing unit that develops a latent image formed by a plurality of light beams scanned on the image carrier with a plurality of color developers in a surface sequential manner. Image forming device. 7. A plurality of light emitting means for emitting a plurality of light beams modulated based on predetermined color image information, and a plurality of light beams are deflected and scanned on an image carrier with a predetermined time difference. An optical scanning unit in which a plurality of rotating polygon mirrors are stacked along the rotation axis direction with a predetermined angular deviation, a first driving unit for rotating the optical scanning unit at a predetermined speed, and the image carrier And a second driving means for driving the rotation at a predetermined speed, wherein the first position is detected by detecting a light beam scanned by any one of the plurality of rotating polygon mirrors. A first detection step of outputting a signal; a second detection step of detecting a predetermined position of the image carrier that is rotationally driven by the second driving means and outputting a second position signal; 2 position signal and the first position A deriving step of deriving a phase difference from a signal, and a switching step of switching a data transmission order of color image information to modulate each light emitting unit based on the phase difference derived by the deriving unit for each color image formation. An image forming method for an image forming apparatus, comprising: 8. A plurality of light emitting means for emitting a plurality of light beams modulated based on predetermined color image information; a plurality of optical scanning means for deflecting and scanning each light beam on an image carrier; A plurality of first rotating means for rotating each optical scanning means at a predetermined speed;
Driving means; scanning control means for controlling the driving of each first driving means such that the phase difference of each light beam scanned by each optical scanning means becomes の of the main scanning period; A first detection unit that detects a light beam scanned by one of the polygon mirrors and outputs a first position signal; a second driving unit that rotates the image carrier at a predetermined speed; A second detection unit that detects a predetermined position of the image carrier that is rotationally driven by a second driving unit and outputs a second position signal; and the second detection unit that is output from the second detection unit. Deriving means for deriving a phase difference between a position signal and the first position signal output from the first detecting means; and each light emitting means should be modulated based on the phase difference derived by the deriving means. The color image information data transmission order is changed for each color image formation. An image forming apparatus comprising: the control means for Toggles control, the.