JP2001219595A - Image forming apparatus and method for controlling image forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high quality color image having no color shift by a method wherein a writing start position of each color in the image on a recording medium is allowed to be consistent with the position of initial color by preventing reading or writing timings to or from a memory for storing image data from being shifted by each of the colors. SOLUTION: A phase difference between a sub-scanning start signal generated in synchronism with rotation of a photosensitive drum 5014 and a main scanning start signal generated by detecting a light beam scanned by a rotary polygon mirror is detected by means of an ITOP sensor A, B. The output timing of the sub-scanning start signal is delayed to be adjusted by a phase adjusting circuit 5017.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and an image forming control method for forming a multicolor image by sequentially superimposing images for each color component based on document image information to be read.

[0002]

2. Description of the Related Art Conventionally, as a color image forming apparatus which prints out color image data, a line is scanned by a main scanning means such as a laser beam printer (LBP) which scans a photosensitive member with a rotating polyhedron by irradiating laser light. Each latent image is formed on a photoconductor, and the latent image is formed for each color element using a developer of a color element such as magenta (M), cyan (C), yellow (Y), black (BK), or the like. 2. Description of the Related Art There is known an apparatus that forms a color image by forming an image and transferring the image for each color element in a superimposed manner on a sheet fixed on a transfer drum.

There is also a system in which an image for each color element formed on a photoreceptor is temporarily overlaid on an intermediate transfer member, and the color image on the intermediate transfer member is collectively transferred to a sheet.

In these apparatuses, the photosensitive member and the transfer drum or the intermediate transfer member are driven at a constant speed in a direction perpendicular to the main scanning direction (sub-scanning direction), and the photosensitive drum, the transfer drum and the intermediate transfer member make one rotation. The colors are superimposed on the paper on the transfer drum and the intermediate transfer body one by one in synchronization with the sub-scanning start signal generated every time.

Further, there is a system in which an image for each recording color element is formed on a photoreceptor in a superimposed manner and is collectively transferred to recording paper. In the above-described color image forming technique, a method of controlling a position at which each color image is superimposed is important in order to prevent a deterioration in image quality of a color image due to a shift of a superposition position of each color image.

As an example of this position control method, the number of main scanning start signals (BD signals) obtained during one rotation of the photosensitive member or the intermediate transfer member and the number of main scanning recording line signals synchronized therewith become an integer. (See FIG. 15 described later).
(See (b)), a method of synchronizing the rotation of a motor for driving a photoconductor or an intermediate transfer member and a scanner motor for driving main scanning has been proposed. Hereinafter, the configuration of the integer line is shown in FIG.
This will be described with reference to FIG.

FIG. 15 is a view for explaining a state of a sub-scanning start signal generation position in a conventional image forming apparatus.

In FIG. 15, (a) shows that the number of main scanning start signals (BD signals) obtained during one rotation of the photosensitive member or the intermediate transfer member and the number of main scanning recording line signals synchronized therewith are n +
This is an example of a configuration in which the number of the photoconductors 1301 is reduced to 1/2.
... Corresponding to the (n-1) th line, the nth line, the first line of the second rotation, and the main scanning recording line signal position.

Reference numeral 1302 denotes an ITOP sensor, which is a photosensitive member 13
01 generates a sub-scanning start signal at a predetermined position according to one rotation. Since the main scanning recording line signal is n + 1/2 lines for each rotation of the photoconductor, that is, every time the ITOP signal is generated, as shown in the drawing, the first line of the first rotation and the first line of the second rotation are shown. Causes a shift of a half line of a fraction.

In order to prevent the above problem, in the prior art, the number of main scanning start signals (BD signals) obtained during one rotation of the photosensitive member or the intermediate transfer member and the number of main scanning recording line signals synchronized therewith are an integer number. Figure 1 shows how to configure
5 (b).

FIG. 15B shows a state in which the number of main scanning start signals (BD signals) obtained during one rotation of the photosensitive member or the intermediate transfer member and the number of main scanning recording line signals synchronized therewith are n. This is an example of a configuration.

The first line, the second line,..., The (n−1) th line, the nth line, and the second line when the photosensitive member 1301 makes two rotations
It corresponds to the first line of the rotation and the position of the main scanning recording line signal.

Since the main scanning recording line signal is n lines for one rotation of the photosensitive member, that is, for each ITOP signal, the first line of the first rotation and the first line of the second rotation are shifted as shown in FIG. Without overlapping.

Next, a description will be given of a method of setting the rotation cycle of the motor for driving the photosensitive member and the intermediate transfer member and the scanner motor for driving the main scanning.

FIG. 16 is a diagram for explaining the configuration of motor drive control in a conventional image forming apparatus, and corresponds to a control example of a motor for driving a photosensitive member or an intermediate transfer member by dividing the BD signal.

In FIG. 16, reference numeral 1401 denotes a photosensitive member, and a photosensitive member driving motor 14
07 is rotationally driven. Reference numeral 1402 denotes a scanner motor, which is controlled to rotate at a constant speed by a PLL circuit 1410 based on a reference clock supplied from an oscillator 1411, rotates a polygon mirror 1403, and drives a laser 140.
The laser beam emitted from the line 4 is line-scanned on the surface of the photoconductor 1401 via a lens 1405.

A beam detection sensor 1406 is disposed in a non-image area on a line scanning line of a laser beam, and generates a main scanning start signal (BD signal) synchronized with the rotation of the scanner motor 1402 for each laser line scanning.

The BD signal is supplied to a photosensitive member driving motor 1407.
The rotation of the scanner motor 1402 and the rotation of the photosensitive member driving motor 1401 can be synchronized by using the reference clock of the PLL circuit 1409 that performs the constant speed control of the above.

The number of the main scanning start signal (BD signal) obtained during one rotation of the rotating body or the intermediate transfer body and the number of main scanning recording line signals synchronized with the main scanning start signal (BD signal) become integers. By doing so, the rotation of the motor for driving the photoconductor 1401 and the rotation of the scanner motor for driving the main scanning are synchronized, so that the alignment can be performed without any displacement regardless of the rotation of the photoconductor and the intermediate transfer body. Becomes possible.

The color image data to be recorded can be obtained by scanning a color original a plurality of times with an original reading device.

Hereinafter, an example of a data reading and writing method in a conventional image forming apparatus will be described with reference to FIGS.

FIGS. 17 and 18 show a main scanning synchronizing signal and an ITOP of the first and second colors in a conventional image forming apparatus.
4 is a timing chart showing timings of scanning signals, read data, write data, and an optical system.

In FIG. 17, the main scanning synchronization signal B
The D signal is generated at a period T in synchronization with the rotation of the scanner motor. Here, ITO which is a drum rotation position signal is used.
The P signal occurs at an arbitrary position in the period of the BD signal. The optical system starts to start when the ITOP signal changes from the “H” state to the “L” state, and the next BD
The CCD starts taking in line data in synchronization with the BD signal from the time when the signal is generated.

FIG. 19 shows C in the conventional image forming apparatus.
FIG. 4 is a diagram for explaining an operation of capturing line data of a CD.

In FIG. 19, the CCD light accumulation / transfer control signal is synchronized with the BD signal, and after light accumulation (data fetch) for a predetermined time (control signal H section), the data light accumulated for a predetermined time is transmitted to the transfer section. Send (control signal L part). The line data sent to the transfer unit is transferred during the next light accumulation, and is output as write data with a delay of one line (1 BD cycle) from the light accumulation.

As shown in FIG. 19, the CCD light accumulation / transfer control signal repeats light accumulation and transfer to the transfer section in synchronization with the BD cycle as shown. The portion of the control signal is a light accumulation section. At this time, the CCD accumulates data of the document currently being scanned by the optical system, that is, the captured data D1 in the drawing.

Next, in the part of the control signal, the data read in the part is transferred to the transfer unit. Further, in the portion of the control signal at which the control signal becomes "H" again, the data of the original being scanned by the optical system, that is, the read data D2 shown in FIG. Is output as write data D1.

The same operation is repeated after the control signal portion, and the line is read out and output line by line in synchronization with the BD signal.

In FIG. 17, a main scanning synchronizing signal is generated after a time T1 when the first color ITOP is inputted, and reading of data of the first line is started therefrom. At that time, the position on the document that the optical system is scanning is
The position of A shown in FIG.
1 position.

At this position, the read data of the first line read out is output as write data of the first line from the CCD with a delay of one line. At this time, the beam scanning position on the drum surface is V × The scanning is performed at the position of T (one line delay by CCD) + V × T1, and the position is shifted by 1 from the writing start position of the first color shown in FIG.
Write the line write data on the drum surface.

Next, the read / write operation of the second color will be described.

After a time T2 when the second color ITOP signal is input, a main scanning synchronization signal is generated.
Reading of the data of the line starts. At this time, the position on the document scanned by the optical system is the position indicated by B in FIG.
, That is, the position of V × T2 from the leading edge of the document.
The read data of the first line read at this position is output as write data of the first line from the CCD with a delay of one line. At this time, the beam scanning position on the drum surface is changed to V × T (CCD The scanning is performed at the position of + V × T2, and the writing data of the first line from the writing start position of the second color shown in FIG. 18 is written on the drum surface.

Thus, in FIG. 18, the first color is the data read at point A of the document and written out from A 'on the drum, and the second color is the data read at point B of the document from point B' on the drum. Has been written out.

Here, the left end of the original shown in FIG.
Assuming that the position of V × T from the generation position of the I, TOP signal on the drum surface is the paper TOP, A and A ′ and B and B ′ are at the same position when viewed from the original TOP and the paper TOP. Since the optical system scanning speed is the same, the original read in the same relationship is written on the drum surface at the same position as the read position, and the first color,
The time difference (T1−T2) between the start of reading of the second color is only the shift of the writing start position from the paper TOP, that is, the difference of the margin, and there is no shift in the position of the subsequent image.

[0035]

However, when the read image data is written to the memory once and then read out and recorded, the phase difference between the read main scan synchronization signal and the write main scan synchronization signal, and the read main scan. The phase shift between the synchronization signal and the sub-scanning synchronization signal becomes a problem.

A description will now be given of a slight phase shift between the sub-scanning synchronization signal and the main scanning synchronization signal, and a shift in the write / read data of the memory.

The rotation speed of the photoreceptor slightly fluctuates due to the effect of additional fluctuation and back crash of the drive transmission gear. Due to this speed fluctuation, a fluctuation occurs in the phase difference between the main scanning start signal and the sub-scanning start signal, and in the conventional technique of always keeping the position of the laser scanning line of the photoconductor constant,
The variation will appear as a color shift.

This variation can be suppressed to a fraction of a line by a method such as minimizing the load variation of the motor or improving the accuracy of the mechanical drive transmission system.
However, when the generation phase of the sub-scanning start signal for each of the recording colors of the color superimposition occurs across the main scanning start signal, one line is actually shifted even though it is shifted by a fraction of a line. Deviation occurs.

For example, as shown in FIG. 20, this is the case where the sub-scanning start signal is generated slightly before and after the main scanning start signal.

FIG. 20 is a diagram for explaining the image forming timing in the main scanning direction and the sub-scanning direction in the conventional image forming apparatus. In accordance with the rotation of the photosensitive member 1901, the sensor flag 1902 shields the unshown ITO sensor from light. This is an example in which a sub-scanning start signal is generated, but its generation position is shifted slightly before and after the main scanning start signal at the first rotation and the second rotation.

Since the first rotation is generated shortly before the main scanning start signal, the main scanning start signal is scanned on the first line, the main scanning start signal is scanned on the second line, and so on. .

However, since the second rotation occurs a little after the main scanning start signal, the main scanning start signal cannot be recognized and the main scanning start signal is the first line and the main scanning start signal is the second line. The eye and the photosensitive member are scanned, causing a shift between the first rotation and the one line.

FIG. 21 is a diagram showing the relationship between the phase relationship between the main scanning synchronization signal, the writing main scanning synchronization signal, and the sub-scanning synchronization signal in the conventional image forming apparatus and the relationship between the memory contents.
An example of a case where a document is temporarily stored in a reading memory for the first and second colors and then read as recording data will be described.

In FIG. 21, the squares on the document are in units of one pixel, and the numbers written therein indicate the positions of the pixels in the sub-scanning direction. First, the reading and writing operations of the first color will be described.

The sub-scanning synchronization signal of the first color is generated immediately before the main scanning synchronization signal for reading the first color. = Write to the memory as data D1. Therefore, for the first color, one line is read from the pixels of the document and stored in the memory. Next, when reading from the memory and performing the writing operation, the main scanning synchronization signal is generated slightly before the sub scanning synchronization signal. In this case, the reading position is delayed by one line from the actual document position because the reading is performed from the memory after the predetermined number n has been counted based on the sub-scanning synchronization signal. Next, the reading and writing operations of the second color will be described.

First, the reading main scanning synchronization signal for the second color is generated slightly before the sub-scanning synchronization signal. Since the reading main scanning synchronization signal for the first color is generated a little after the sub-scanning synchronization signal, the actual phase shift is slight.
In the memory write data of the color, a pixel delayed by one line from the color of the first color is set as data D1 of the first line.

Further, similarly, the memory read main scanning synchronization signal of the second color is generated immediately after the sub scanning synchronization signal, and
The memory is read out one line faster than the first color. As described above, by using different signals having no synchronous relationship between the reading main scanning synchronization signal and the writing main scanning synchronization signal, and by having slight fluctuations in the phases of the main scanning synchronization signal and the sub-scanning synchronization signal, 2 Since the color is written into the memory one line later than the first color and read out from the memory one line faster, there is a possibility that a total of about two lines of positional shift may occur.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a sub-scanning start signal generated in synchronization with the rotation of an image carrier and scanning by a rotary polygon mirror. By detecting a phase difference from a main scanning start signal generated by detecting a light beam, and adjusting the output timing of the sub-scanning start signal based on the detection result, Even if it occurs at the timing, the sub-scanning start signal can always be adjusted to be centered on the center of the cycle of the main scanning start signal, and even if the phase difference between the sub-scanning start signal and the main scanning start signal fluctuates slightly, the image data can be adjusted. The read / write timing of the memory in which the color is to be stored does not shift for each color, and the write start position of the image of each color on the recording medium is matched with the position of the first color, so that a high quality color without color shift It is to provide an image forming apparatus and an image forming control method image can be obtained.

[0049]

According to a first aspect of the present invention, there is provided an image forming apparatus for forming a multicolor image by sequentially superimposing images of respective color components based on read original image information. Reading means (CC shown in FIG. 5)
D501) and a memory (memory 5 shown in FIG. 5) for storing original image information read by the reading unit.
06), a sub-scanning start signal output means (corresponding to ITOP sensors A and B shown in FIG. 5) for generating a sub-scanning start signal in synchronization with the rotation of the driven image carrier, and the color components Scanning means (polygon mirror 5013 shown in FIG. 5) for deflecting a light beam modulated based on each image information and scanning on an image carrier which is rotationally driven by the driving means
Main-scanning start signal output means (corresponding to the BD sensor 5015 shown in FIG. 5) for detecting the light beam to be scanned and generating a main-scanning start signal; Delay means for delaying the sub-scanning start signal by a predetermined time based on a phase difference between the sub-scanning start signal and the main scanning start signal when writing or reading document image information in the memory in synchronization with (Corresponding to the phase matching circuit 5017 shown in FIG. 5).

According to a second aspect of the present invention, the delay means delays the sub-scanning start signal so that the sub-scanning start signal is aligned with the center of the main scanning start signal cycle.

According to a third aspect of the present invention, the delay means adjusts the sub-scanning start signal at the predetermined timing so as to match the sub-scanning start signal within a predetermined area within the main scanning start signal cycle. It is to delay.

According to a fourth aspect of the present invention, in the predetermined area within the main scanning start signal cycle, the center of the main scanning start signal cycle corresponding to the phase variation between the main scanning start signal and the sub-scanning start signal is set. Is an area centered at.

According to a fifth aspect of the present invention, the sub-scanning start signal output means outputs the sub-scanning start signal twice each time the image carrier makes one rotation.

According to a sixth aspect of the present invention, there is provided an image forming apparatus for sequentially superimposing images of respective color components on the basis of read document image information to form a multicolor image, a reading means for reading the document image (FIG. (Equivalent to CCD 501 shown in Fig. 5)
A memory for storing document image information read by the reading means (corresponding to the memory 506 shown in FIG. 5);
Driving means (corresponding to a drum motor 5016 shown in FIG. 5) for rotating the image carrier, and a sub-scanning start signal for generating a sub-scanning start signal in synchronization with the rotation of the image carrier driven by the driving means Output means (corresponding to the ITOP sensors A and B shown in FIG. 5) and a light beam modulated based on image information for each of the color components are deflected to scan on an image carrier rotated and driven by the driver. And a main scanning start signal output unit (corresponding to the BD sensor 5015 shown in FIG. 5) for detecting the scanned light beam and generating a main scanning start signal. ,
When writing and reading document image information in the memory in synchronization with the sub-scanning start signal and the main scanning start signal, based on a phase difference between the sub-scanning start signal and the main scanning start signal, And a delay means (corresponding to the phase matching circuit 5017 shown in FIG. 5) for delaying the sub-scanning start signal for a predetermined time.

According to a seventh aspect of the present invention, there is provided a reading means for reading a document image, and a memory for storing document image information read by the reading means, wherein each color component is stored based on the read document image information. An image forming control method for an image forming apparatus for forming a multi-color image by sequentially superimposing images, wherein sub-scanning is performed in synchronization with the rotation of the image carrier driven by a driving unit that rotationally drives the image carrier. A sub-scanning start signal output step for generating a start signal (step (5) shown in FIG. 9), and a light beam modulated based on image information for each color component is deflected and driven to rotate by the driving means. A main scanning start signal output step (steps (6) and (7) shown in FIG. 9) for scanning the image carrier and detecting the scanned light beam to generate a main scanning start signal; Start signal When writing or reading document image information in the memory in synchronization with the main scanning start signal, the sub scanning start signal is generated based on a phase difference between the sub scanning start signal and the main scanning start signal. A delay process for delaying a predetermined time (steps (8) to (1) shown in FIG. 9)
0)).

According to an eighth aspect of the present invention, in the delaying step, the sub-scanning start signal is delayed such that the sub-scanning start signal is aligned with the center of the main scanning start signal cycle.

According to a ninth aspect of the present invention, in the delay step, the sub-scanning start signal is adjusted so that the sub-scanning start signal at the predetermined timing falls within a predetermined area within the main scanning start signal cycle. It is to delay.

According to a tenth aspect of the present invention, in a predetermined area within the main scanning start signal cycle, the center of the main scanning start signal cycle corresponding to the phase variation between the main scanning start signal and the sub-scanning start signal is set. Is an area centered at.

According to an eleventh aspect of the present invention, in the sub-scanning start signal output step, the sub-scanning start signal is output twice each time the image carrier makes one rotation.

According to a twelfth aspect of the present invention, there is provided an image forming control method in an image forming apparatus for forming a multicolor image by sequentially superimposing images for each color component based on document image information to be read. Reading step of reading an image (FIG. 8)
, A storage step (not shown) for storing the document image information read in the reading step in a memory, a driving step (not shown) for driving the image carrier to rotate, and the driving step performed by the driving step. A sub-scanning start signal output step (step (5) shown in FIG. 8) for generating a sub-scanning start signal in synchronization with the rotation of the image carrier, and a light beam modulated based on the image information for each color component. A scanning step of scanning the image carrier that is deflected and rotated by the driving step, and a main scanning start signal output step of detecting the scanned light beam and generating a main scanning start signal (FIG. 8).
(6), (7)), when writing and reading original image information in and from the memory in synchronization with the sub-scanning start signal and the main scanning start signal, A delay step of delaying the sub-scanning start signal by a predetermined time based on the phase difference from the main scanning start signal (FIG. 8)
(8) to (10)).

[0061]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG. 1 is a sectional view for explaining the structure of an image forming apparatus according to a first embodiment of the present invention.

In the figure, reference numeral 201 denotes an image scanner which reads a document and performs digital signal processing. 200
A printer unit prints a full-color image of a document read by the image scanner unit 201 or an image based on image data transferred from an external device such as a computer (not shown) via a predetermined communication medium on recording paper.

In the image scanner section 201, 20
An original pressing plate 2 presses the original 204 on the original platen glass 203 onto the original platen glass 203. Reference numeral 205 denotes a halogen lamp which irradiates a document 204 on a document table glass 203 with light.

Reference numeral 210 denotes a three-line sensor (hereinafter, CCD)
And a red (R) sensor 210-1, a green (G) sensor 210-2, and a blue (B) sensor 210-3.
7. Lens 208 including far-infrared cut filter 231
The color information of the light information formed on the CCD 210 through the color separation is separated into red (R), green (G),
Read the blue (B) component. 209 is a signal processing unit,
The R, G, and B signals read by the R, G, and B sensors 210-1 to 210-3 are electrically processed to obtain magenta (M), cyan (C), yellow (Y), and black (B).
K) is decomposed into components and sent to the printer unit 200.

Reference numeral 211 denotes a standard white plate, which is composed of R, G, B
The sensors 210-1 to 210-3 generate correction data of the read data. The standard white plate 211 has substantially uniform reflection characteristics from visible light to infrared light, and has white color when visible. R, G, B using this standard white plate
The output data of the visible sensors of the sensors 210-1 to 210-3 is corrected. An optical sensor 230 is a flag plate 229.
In addition, an image tip signal VTOP is generated.

In the printer unit 200, reference numeral 101 denotes an image writing timing control circuit,
01 and a semiconductor laser 102 based on magenta (M), cyan (C), yellow (Y), and black (BK) image signals input from an external device such as a computer (not shown) via a predetermined communication medium. Drive modulation. 103
Is a polygon mirror, which is driven to rotate by the polygon motor 106, reflects the laser beam emitted from the semiconductor laser 102, and reflects the f-θ lens 104 and the return mirror 216.
Scans on the photosensitive drum 105 via the.

The photosensitive drum 105 is a polygon mirror 10
3 forms an electrostatic latent image by laser scanning. 107
Is a BD sensor, which is provided near the scanning start position of one line of laser light, detects line scanning of laser light, and outputs a main scanning start signal (scanning start reference signal (B
D signal)).

219 is a magenta (M) developing device, 220 is a cyan (C) developing device, 221 is a yellow (Y) developing device,
A black (BK) developing unit 222 develops an electrostatic latent image on the photosensitive drum 105 to form a toner image. Reference numeral 108 denotes a transfer drum, which is a paper cassette 224 or 2
The recording paper 109 fed from the printer 25 is conveyed by suction, and the toner image formed on the photosensitive drum 105 is transferred onto the recording paper 109.

Reference numeral 110 denotes an ITO sensor, which is a transfer drum 1
08, the passage of the flag 111 fixed in the transfer drum 108 is detected, and a sub-scanning start signal for each color (a signal indicating the leading end position of the recording paper 109 adsorbed on the transfer drum 108 (ITOP signal)) ). 22
A fixing unit 6 fixes the toner image transferred onto the recording paper 109 by the transfer drum 108.

The operation of each section will be described below.

The original 204 on the original platen glass 203 is irradiated with light from a halogen lamp 205, and reflected light from the original 204 is guided to mirrors 206 and 207,
Forms an image on the CCD 210. Next, the CCD 210
Reads the red (R), green (G), and blue (B) components of the full-color information and sends it to the signal processing unit 209. Note that the halogen lamp 205 and the mirror 206 operate at the speed “v” and the mirror 2
Reference numeral 07 scans the entire surface of the document by mechanically moving the line sensor at a speed “v / 2” in a direction perpendicular to the electrical scanning direction (hereinafter, the main scanning direction) of the line sensor (hereinafter, the main scanning direction).

Further, using the standard white plate 211, R, G,
The output data is corrected by the visible sensors of the B sensors 210-1 to 210-3. Further, the optical sensor 230 generates the image leading edge signal VTOP together with the flag plate 229. The signal processing unit 209 electrically processes the read R, G, and B signals to separate them into magenta (M), cyan (C), yellow (Y), and black (BK) components. Send to

It should be noted that M, C, Y, and BK per one original scanning (scan) in the image scanner unit 201.
Of these, one component is sent to the printer unit 200, and one printout is completed by a total of four document scans.

An image signal sent from an external device such as a computer (not shown) via the image scanner unit 201 or a predetermined communication medium is sent to the image writing timing control circuit 101. The image writing timing control circuit 101 modulates and drives the semiconductor laser 102 according to magenta (M), cyan (C), yellow (Y), and black (BK) image signals. The laser light emitted from the semiconductor laser 102 is reflected by the rotating polygon mirror 103, fθ-corrected by the f-θ lens 104, is reflected by the return mirror 216, scans the photosensitive drum 105, and scans the photosensitive drum 105. An electrostatic latent image is formed.

Further, while the photosensitive drum 105 rotates four times, the four developing machines 219 to 222 are alternately operated by the photosensitive drum 10.
5, M, C, and C formed on the photosensitive drum 105.
Develop with toner corresponding to the electrostatic latent images of Y and BK. Recording paper 10 fed from paper cassette 224 or 225
9 is wound around the transfer drum 108, and after the four colors of M, C, Y, and BK of the toner image developed by the developing machine are sequentially transferred, the recording paper 109 is discharged through the fixing unit 226. .

FIG. 2 is a diagram for explaining the configuration of the printer unit 200 of the image forming apparatus shown in FIG. 1. The same components as those in FIG. 1 are denoted by the same reference numerals.

In the figure, reference numeral 112 denotes an oscillator which outputs a clock having a predetermined frequency. A frequency dividing circuit 113 divides a clock output from the oscillator 112 by a predetermined frequency dividing ratio and transmits a polygon motor driving pulse (reference CLK-P). Reference numeral 114 denotes a PLL circuit which controls the polygon motor 10
FG pulse output along with rotation of No. 6 and reference C
The FG pulse and the reference CLK are adjusted so that the phase of LK-P matches.
−P which detects the phase difference and frequency deviation of −P, compares them, and controls the drive voltage to the polygon motor 106.
L control is performed.

Reference numeral 121 denotes an oscillator which outputs a clock having a predetermined frequency. A laser lighting signal generation circuit 120 inputs a clock from the oscillator 121 and a BD signal from the BD sensor 107, and outputs a laser lighting signal for detecting a BD signal. Reference numeral 122 denotes a phase matching circuit which is an ITOP signal from the ITOP sensor 110 and a B signal from the BD sensor 107.
The D signal, the data load enable signal from the CPU 130 and the like are input, and the ITOP signal is delayed and output (phase matching) based on the phase difference between the ITOP signal and the BD signal.

An image writing timing control circuit 101 receives an ITOP signal output from the phase matching circuit 122 and outputs an image signal at a timing synchronized with the ITOP signal. Reference numeral 117 denotes an OR gate which outputs an image signal from the image writing timing control circuit 101 or a laser lighting signal for BD signal detection from the laser lighting signal generation circuit 120 to the semiconductor laser 102,
2 is modulated.

A frequency dividing circuit 119 divides the BD signal from the BD sensor 107 at a predetermined frequency dividing ratio and transmits a photosensitive drum motor driving pulse (reference CLK). 118 is P
The LL circuit detects a phase difference and a frequency deviation between the FG pulse and the reference CLK so that the phase of the motor FG pulse output with the rotation of the photosensitive drum motor 115 matches the phase of the reference CLK, and compares the detected phase difference and frequency deviation. Drum motor 115
PLL control for controlling the drive voltage to the controller is performed. Note that CP
U130 has a ROM and a RAM inside, and performs overall control of the entire image forming apparatus based on a program stored in the ROM.

Hereinafter, the operation of each section will be described.

An image signal transferred from the image scanner unit 201 shown in FIG. 1 or an external device such as a computer (not shown) via a predetermined communication medium is sent to the image writing timing control circuit 101, and the image writing timing The control circuit 101 supplies the magenta (M), cyan (C), yellow (Y), and black (B
The semiconductor laser 102 is modulated and driven according to the image signal K). The laser light is reflected by the rotating polygon mirror 103, fθ-corrected by the f-θ lens 104, reflected by the return mirror 216 (shown in FIG. 1), scans the photosensitive drum 105, and scans the photosensitive drum 105. An electrostatic latent image is formed.

The clock of the oscillator 112 is divided by the frequency dividing circuit 113
The polygon motor driving pulse (reference CLK-P) generated by dividing the frequency is sent to the PLL circuit 114. PLL
The circuit 114 includes a motor FG from the polygon motor 106.
The phase difference and the frequency deviation between the FG pulse and the reference CLK-P are detected so that the phase of the pulse and the reference CLK-P match, and PLL control for controlling the drive voltage to the polygon motor 106 is performed by comparing them.

The BD sensor 107 provided near the scanning start position of one line of the laser beam detects the line scanning of the laser beam, and a scanning start reference signal (refer to FIG. 3 described later) of each line of the same period. BD signal). Also,
An ITOP sensor 110 in the transfer drum 108 detects a flag 111 fixed in the transfer drum 108 by rotation of the transfer drum 108, and an ITOP signal for each color (recording on the transfer drum 108) as shown in FIG. Paper 1
09 indicating the position of the tip of 09). Further, the photosensitive drum motor 115 includes a laser lighting signal generation circuit 120.
The laser lighting signal for BD signal detection from the frequency dividing circuit 11
The motor driving pulse (reference CLK) divided by 9 is PL
The rotation is driven by being sent to the L circuit 118.

The PLL circuit 118 includes the photosensitive drum motor 1
The phase difference and the frequency deviation between the FG pulse and the reference CLK are detected so that the phase of the motor FG pulse from the reference 15 and the phase of the reference CLK coincide with each other.
PLL control for controlling the drive voltage to 5 is performed. The photosensitive drum 105 is rotationally driven by a photosensitive drum motor 115 via a gear belt 116 in the direction of the arrow. Since the transfer drum 108 is connected to the photosensitive drum 105 via a gear (not shown), the transfer drum 108 synchronizes with the photosensitive drum 105 at the same speed as the arrow. (Sub-scan)
Drive in the direction. The BD signal and the ITOP signal are input to the image writing timing control circuit 101, and send the image signal to the semiconductor laser 102 at the following timing, for example. That is, after detecting the rise of the ITOP signal, the image writing timing control circuit 10
1 counts the BD signal a predetermined number of times, and outputs the “n” th BD signal
A sub-scanning start signal is generated (for "m" BD signals determined by the length of the recording paper 109) in synchronization with the rise of the signal, and the image signal is irradiated onto the photosensitive drum 105 as laser modulated light.

FIG. 3 is a timing chart showing image forming timing of the printer section 200 of the image forming apparatus shown in FIG.

In the figure, an ITOP signal is sent from an ITOP sensor 110 in the transfer drum 108 to the transfer drum 108.
The flag 1 fixed in the transfer drum 108 by the rotation of
Transfer drum 108 output by detecting 11
This signal indicates the position of the leading edge of the upper recording sheet 109, and is output for each color.

The BD signal is a scanning start reference signal for each line of the same cycle, which is output when the BD sensor 107 provided near the scanning start position of one line of the laser beam detects the line scanning of the laser beam. It is.

As for the image signal, the BD signal and the ITOP signal are input to the image writing timing control circuit 101. For example, after detecting the rising of the ITOP signal, the OR gate is synchronized with the rising of the “n” th BD signal. The laser beam is transmitted to the semiconductor laser 102 via 117. That is, ITOP
After detecting the rise of the signal, a sub-scanning start signal is generated in synchronization with the rise of the “n” th (predetermined number) BD signal, and the image signal is laser-modulated for the “m” th BD signal. The light is irradiated on the photosensitive drum 105 as light.

In the present embodiment, exactly an integer number of BD signals are output during one rotation of the photosensitive drum 105 so that the scanning light of the laser on the photosensitive drum 105 is always at the same position every rotation. The number of BD signals output during one rotation of the photosensitive drum determined from the process speed and the resolution is “8192”.

The gear ratio is such that the photosensitive drum motor 115 makes "64" rotations while the photosensitive drum 105 makes one rotation.
Since the number of FG pulses per rotation is “32”, the photosensitive drum motor 115 outputs
One rotation requires 32 pulses of the reference clock.

Therefore, in order for the photosensitive drum 105 to make one rotation, the reference clock must be “64 rotations × 32 pulses = 204 pulses”.
"8 pulses" are required. Therefore, the BD signal is changed to “1 /
By dividing the frequency by "4" and using it as the reference CLK of the photosensitive drum motor 115, the photosensitive drum 105 makes one rotation when 8192 BD signals are output. In addition,
This gear ratio is configured to be a natural number. This is because the monitor and the reduction gear are rotated by an integer while the photosensitive drum 105 makes one rotation, so that the motor shaft and reduction gear for each rotation of the photosensitive drum 105 are knitted. This is because the effect of the mind is always the same, and the color shift due to these eccentricities is reduced to zero.

FIG. 4 is a block diagram illustrating the configuration of an image memory in the image forming apparatus according to the present invention.

In the figure, reference numeral 401 denotes a sub-scanning address counter, which supplies an address for each line to the memory 403 using a reader LSNC, that is, a reading synchronization signal as a count. This counter uses the sub-scanning synchronization signal ITOP.
, A count value for a predetermined paper length is loaded, and every time the reader LSNC is input after the sub-scan synchronization signal ITOP is input, a down-count is performed and the address of the sub-scan of the image data is supplied.

Reference numeral 402 denotes a main scanning address counter, which is cleared each time a reader LSYNC of a one-line main scanning synchronizing signal is inputted, and the memory 403 uses the video CLK as a count.
Is supplied with an address for each pixel. The memory 403 is
Writing and reading of image data are performed based on the addresses given from the counters 401 and 402. Here, the reader LSYNC is the same signal at the time of writing and at the time of reading, and is synchronized with the BD signal. Write permission to the memory 403 is enabled at the enable terminal (WE terminal) of the memory 403.
Is set to “H” by a CPU (not shown).

With reference to FIG. 5, a description will be given, with reference to FIG. 5, of a method of performing a write operation in which read image data is once written in a memory and then read from the memory in the above-described configuration.

FIG. 5 is a block diagram for explaining the configuration of the phase matching control in the image forming apparatus according to the present invention. Hereinafter, the configuration and operation will be described.

In FIG. 5, the RGB color analog data read by the CCD 501 is transmitted to the A / D converter 5.
02, and are A / D converted into RGB digital data, respectively.
Is converted into MCYK density data and transferred to the data selector (SEL1) 504. The data selector 504 sends 2-bit color code data COL <1. . 0>, for example, COL
<1. . 0> = 00, M, COL <1. . 0> = 0
When 1, C, COL <1. . Y, C when 0> = 10
OL <1. . When 0> = 11, MCY
The input 4 data of K is switched and the output SEL1OUT is output.

The CPU 505 determines the color for which the image is to be formed at present, and sequentially determines the color code data COL <1. . 0>.

The output SEL1OUT from the data selector 504 is output to and stored in the memory 506 and the data selector (SEL2) 507.

The memory 506 has, for example, 400 DPI
, So that image data for A3 can be recorded. This memory stores 1 in the address indicated by the main scanning address counter 508 and the sub-scanning address counter 509 sequentially.
Data is recorded pixel by pixel. The memory enable signal WE is controlled by the CPU 505,
"H" is output when recording is performed, and "L" is output when reading is performed.

The main scanning address counter 508 clears the counter value to “0” every time the main scanning synchronization signal BD is generated, and outputs the image clock C output from the crystal oscillator 5010.
It functions as an up counter that counts the rising edge of LK, and the count value is the main scanning synchronization signal BD.
Is a value indicating the pixel address in the main scanning direction with reference to. The sub-scanning address counter 509 is a down counter that loads data of a predetermined pixel length upon generation of the sub-scanning synchronizing signal ITOP and counts one line at a time by counting the rising edge of the main scanning synchronizing signal BD. And the count value is the sub-scanning synchronization signal IT
The value indicates a pixel address in the sub-scanning direction based on OP.

Accordingly, based on the generation of the sub-scanning synchronization signal ITOP, the driving of the scanner motor (not shown) and the CCD
By determining the drive start timing of the drive 501 and the laser driver 501, the image data stored in the memory 506 is converted into the address data indicated by the sub-scanning address counter 509 and the main scanning address counter 508 based on the sub-scanning synchronization signal ITOP. In the ideal system in which the sub-scanning synchronization signal ITOP and the main scanning synchronization signal BD have a perfect synchronization relationship, the output timing of the image data output from the memory 506 is equal to the output SEL1OUT. .

Next, the data selector 507 outputs the output SEL.
1OUT, that is, whether to output a real-time image,
The output of the memory 506, that is, whether to output the image data once stored in the memory is switched. This switch is C
The determination is made by the PU 505, and when selecting the output SEL1OUT, the CPU 505 sets the output control signal VSEL to "0", and when selecting the output OUT of the memory 506, sets the output control signal VSEL to "1".

The image data output from the data selector 507 is converted by a laser driver 5012 into a laser light amount or a laser emission width corresponding to the image data.
4 is illuminated. BD sensor 50 on the position of this irradiation
Reference numeral 15 is provided, and this detection signal becomes a main scanning synchronization signal BD for determining a start timing for each line cycle.

Here, as described above, the frequency of the main scanning synchronizing signal BD is divided by the frequency divider 5011 and the drum driving motor 5016 is divided.
And the number of main scanning synchronization signals BD is an integer (an integer number of lines) in one rotation of the photosensitive drum, so that the main scanning synchronization signals generated from the ITOP sensors A and B by the rotation of the drum drive motor 5016. The signals ITOPA and ITOPB can be synchronized with the sub-scan synchronization signal BD.

In the present embodiment, the main scanning synchronization signal ITOP
There are two main scanning synchronization signals ITOPA and ITOPB, which correspond to the case where two image forming operations are performed with one rotation of the drum.

FIG. 6 shows the correspondence between the image forming position of the drum and the main scanning synchronization signals ITOPA and ITOB at this time.

FIG. 6 shows the photosensitive drum 5014 shown in FIG.
Image forming position and main scanning synchronization signals ITOPA, ITOP
FIG. 6 is a diagram for explaining a correspondence relationship with B.

As shown in FIG. 6, main scanning synchronization signals ITOPA, ITOPB are provided at positions facing the photosensitive drum 5014.
Are provided, and an image is formed from a predetermined distance A with reference to the timing of generation of the main scanning synchronization signal ITOPA.

Similarly, the ITOP sensor B forms an image from a predetermined distance A with reference to the timing at which the main scanning synchronization signal ITOPA is generated. In this manner, two images can be formed by one rotation of the photosensitive drum 5014. These main scanning synchronization signals ITOP
A and ITOPB are input to the phase matching circuit 5017, and are adjusted so that they have a predetermined phase with the main scanning synchronization signal BD.

The adjusted ITOP signal, that is,
By reading and writing the memory from the phase matching circuit 5017 shown in FIG. 5 with reference to the ITOP control signals A-ITOP and B-ITOP,
It is possible to prevent a line shift due to a minute change in the phase of the D signal.

Further, the CPU 505 selectively disables the output of the ITOP control signals A-ITOP and B-ITOP, so that only the main scanning synchronization signal ITOPA, only the main scanning synchronization signal ITOB, or the main scanning synchronization signal ITOPA is performed. , And ITOPB can be switched.

Further, the photosensitive drum 50 at the time of pre-scanning or the like is used.
When it is not necessary to rotate 14, the CPU 505 generates an ITOP signal in a pseudo manner. This means that the data selector (SEL3) 5018 is set to the select signal (ITOPS).
By setting the EL signal) to “H”, it is possible to switch from the default main scanning synchronization signal ITOPA to the switching control signal C-ITOP which is a CPU output, and generate an ITOP signal at an arbitrary timing. This ITOP
The signal is also passed through the phase matching circuit 5017,
The phase of the TOP signal and the phase of the BD signal can be adjusted to a predetermined phase.

Hereinafter, an example of the phase matching method will be described with reference to FIGS.

FIG. 7 shows the phase matching circuit 12 shown in FIG.
8 is a circuit diagram for explaining the configuration of FIG. 2, and FIG. 8 is a timing chart for explaining the operation of the phase matching circuit 122 shown in FIG.

In the figure, reference numeral 601 denotes a rising edge detection circuit for detecting the rising edge of the ITOP signal emitted from the ITOP sensor 110 in the transfer drum 108. 60
Reference numeral 2 denotes an UP counter, which is a free-run counter that is cleared to "0" by a BD signal and repeats the UP count, and the count number of this counter becomes a BD signal cycle.

Reference numeral 603 denotes a latch circuit, and an UP counter 602 is provided at the output timing of the rising edge detection circuit 601.
Latch the output of. Thus, the latched count data indicates the rising edge position of the ITOP signal in the BD signal cycle. That is, the data indicates the phase difference between the ITOP signal and the BD signal.

Here, the output of the rising edge detection circuit 601 and the output of the AND gate 605 for outputting a data load enable signal set by a controller (CPU) not shown are connected to the latch enable terminal LE of the latch circuit 603. When the data load enable signal is at the L level, the latch operation is not performed even if the rising edge of the ITOP signal is detected. And
The latched count data is input to the subtraction circuit 608.

Reference numeral 606 denotes a 3CLK delay circuit which outputs a signal obtained by delaying the ITOP signal by a predetermined time (3CLK in this embodiment) to the AND gate 614. A flip-flop 607 matches the output of the rising edge detection circuit 601 with the clock timing.

A subtraction circuit 608 subtracts the count data latched by the latch circuit 603 from the data set by the CPU 130. In the present embodiment, assuming that the count number of the BD signal cycle (a known value uniquely determined by the device) is T, the setting data is “(3/2) T” which is “1.5” times that of the BD signal. The result of this subtraction processing is the required delay from the input of the ITOP signal to the center of the next BD signal cycle. That is, assuming that the count number of the BD signal cycle is “T = 100” and the ITOP signal is input at the position of the count “80 (= latch data)”, “(3/2) T−80 = 150−80 =
If the ITOP signal is delayed by the "70" count, FIG.
As shown in the figure, ITOP is located at the center position of the next BD signal cycle.
It can be adjusted so that a signal is input.

Reference numeral 612 denotes a data load type down counter (hereinafter referred to as a down counter).
In synchronization with the output of the rising edge detection circuit 601 of the ITOP signal after the timing is adjusted, the subtraction circuit 60
8 is loaded from the data load terminal.

When the down counter 612 finishes counting the loaded data, it outputs an RC output to the JK flip-flop 613. The time counted by the down counter 612 is a delay time for adjusting the phase of the ITOP signal. JK flip-flop 613 is
It is reset at the rising edge of the TOP signal, and the ITOPDLY signal as its Q output becomes the "L" level output, and holds the "L" level state until RC of the down counter 612 is output and set.

That is, the "L" level is maintained for the required delay time from the rise of the ITOP signal. By outputting the ITOPDLY output and a signal obtained by delaying the ITOP signal by a predetermined time (3 CLK in this embodiment) for timing adjustment through the AND gate 614, the ITOP signal can be generated at the center of the BD signal cycle. it can.

Further, only the phases of the BD signal and the ITOP signal in the first rotation are sampled by the above-described data load enable signal, and the delay is performed so that the ITOP signal is generated at the center of the BD signal cycle. By setting the data load enable signal to the “L” level in the rotations to the n-th rotation, the same data as the delay in the first rotation can be held. As a result, the ITOP signal position in the first rotation is generated at the center position of the BD signal period, and the second and subsequent rotations are generated by deviating from the center thereof by a variation due to the rotation accuracy of the photosensitive drum motor and the like.

Hereinafter, the phase matching process of the image forming apparatus according to the first embodiment of the present invention will be described with reference to FIGS.

FIG. 9 is a flowchart showing a phase matching processing procedure of the image forming apparatus according to the first embodiment of the present invention. Note that (1) to (11) indicate each step.

First, when the image forming sequence operation is started, the CPU 130 determines whether or not the operation is the pre-scan operation, and if the operation is the pre-scan operation, sets the data load enable signal to "H" (1).

On the other hand, if it is determined in step (1) that the operation is not the pre-scan operation, the flow advances to step (2) to determine whether the signal is the first (first) ITOP signal, and the first ITOP signal is determined. If it is determined that the signal is not a signal, the data load enable signal is set to the "L" level (data load enable disabled) (4), and the first IT
If it is determined that the signal is an OP signal, the AND gate 60
The data load enable signal input to 5 is set to "H" level (data load enable permission) (3).

Next, the rising edge of the ITOP signal is
It is determined whether or not the signal is detected by the rising edge detection circuit 601 (5). If it is determined that the signal has not been detected, the process returns to step (2).
The state of the data load enable signal is determined (6). If the data load enable signal is determined to be in the enabled state, the phase position of the ITOP signal within the BD signal cycle is latched by the latch circuit 603 (7), Subtraction circuit 608
Assuming that a value set by the CPU 130, for example, the count number of the BD signal cycle (a known value uniquely determined by the apparatus) is T, the phase position latched from 1.5 times (3/2) T The data is subtracted, the data is calculated as the delay amount of the ITOP signal (8), and the calculated delay amount is loaded into the data load type down counter 612, and the ITOP signal delay processing is performed based on the data loaded delay amount. (9), and output a delayed ITOP signal (10).

Next, it is determined whether or not the output sequence has been completed (11). If it is determined that the output sequence has not been completed,
Returning to step (2), if it is determined that the process has been completed,
The process ends (this operation is repeated until the output sequence operation ends).

On the other hand, if it is determined in step (6) that the data load enable signal is not in the enabled state (the data load enable signal is in the disabled state), the I / O is disabled based on the data already latched in the latch circuit 603.
The delay processing of the TOP signal is performed (9), and the delayed ITOP signal is output (10). Next, the CPU 130 determines whether or not the output sequence has been completed (11). If it is determined that the output sequence has not been completed, the process returns to step (2). If it is determined that the output sequence has been completed, the process ends. (This operation is repeated until the output sequence operation is completed.)

FIG. 10 is a timing chart showing a phase matching process of the image forming apparatus according to the second embodiment of the present invention.

In the figure, 1 is set shortly before the main scanning start signal.
When the sub-scanning start signal (ITOP signal) for the rotation is generated, the CPU 130 shown in FIG. 2 sets the data load enable signal to the “H” level, so that the sub-scanning for the first rotation (first color) is started. A signal delay amount A is calculated.
Based on the calculated delay amount A, the sub-scanning start signal for the first rotation is generated at the main scanning synchronization center position with a delay as shown in the figure.

The sub-scanning start signal (ITOP signal) for the second rotation is generated shortly after the main scanning start signal.
Since the PU 130 sets the data load enable signal to the “L” level, the delay amount of the sub-scanning start signal of the second rotation is not calculated, and the delay amount A calculated by the sub-scanning start signal of the first rotation is The second rotation (second
The sub-scanning start signal of (color) also has the delay amount A similarly to the first rotation.
Is generated as shown in FIG.

Similarly, for the n-th rotation (n-th color), the sub-scanning start signal for the n-th rotation is generated by delaying by the delay amount A as shown in FIG.

As described above, the sub-scanning start signal before the delay is
Although it fluctuated before and after the main scanning start signal, by delaying each sub-scanning start signal based on the delay amount A calculated at the first rotation, the fluctuation of the sub-scanning start signal is changed by the period of the scanning start signal. Near the center of With this processing, it is possible to increase the margin for the fluctuation in the sub-scanning direction.

Therefore, if image writing is started based on this ITOP signal, the phase difference between the ITOP signal and the BD signal is always constant for each color, so that the image writing positions of the first to nth colors are accurately adjusted. And a high-quality image without color shift can be obtained.

By setting the position where the ITOP signal is generated at the center of the period of the BD signal, a large margin can be provided for fluctuations caused by uneven rotation of the photosensitive drum motor, and the accuracy of the motor and the driving mechanism can be sufficiently accommodated.

Therefore, if image writing is started based on the ITOP signal, the phase difference between the ITOP signal and the BD signal is always constant for each color, so that the image writing positions from the first color to the nth color can be accurately adjusted. Thus, a high-quality image without color shift can be obtained.

Further, by using the same BD signal at the time of writing and reading, the BD signal at the time of writing can be obtained.
An image shift due to a signal phase shift does not occur. In addition, at the time of pre-scanning for area determination and the like, since it is not necessary to rotate the photosensitive drum, a pseudo I
In order to generate the TOP signal from, for example, a CPU or the like, if the pseudo-ITOP signal is similarly controlled to be generated at the center of the BD cycle, the data written in the memory by the prescan and the data at the time of actually forming an image can be compared. The displacement can be minimized.

[Second Embodiment] In the first embodiment, as a method of synchronizing the photosensitive drum and the scanner motor, a main scanning start signal (BD signal) obtained during one rotation of the photosensitive drum and the intermediate transfer body is used. ) And the number of main-scanning recording line signals synchronized therewith is an integer number,
The same effect may be obtained by using a common clock for the reference clock of the motor that drives the photosensitive drum and the intermediate transfer member and the reference clock of the scanner motor that drives the main scanning. Hereinafter, the embodiment will be described with reference to FIG.

FIG. 11 is a diagram illustrating the configuration of an image forming apparatus according to a second embodiment of the present invention.

In the figure, reference numeral 1001 denotes a photosensitive member, which is rotationally driven by a photosensitive member drive motor (drum motor) 1007 via a drive belt 1008. A scanner motor 1002 is controlled to rotate at a constant speed by a PLL circuit 1010 based on a reference clock supplied from an oscillator 1011 and drives the polygon mirror 1003 to rotate. The polygon mirror 1003 performs line scanning on the surface of the photoconductor 1001 with a laser beam emitted from a laser 1004 via a lens 1005.

Reference numeral 1009 denotes a PLL circuit which controls the photoconductor driving motor 1007 at a constant speed based on a reference clock generated by an oscillator 1011 used for PLL control of the scanner motor 1002.

As described above, the PLL circuit 1009 controlling the photosensitive member drive motor 1007 and the scanner motor 10
By generating both reference clocks of the PLL circuit 1010 controlling the O.02 with the clock generated from the same oscillator 1011, the rotation of the scanner motor 1002 and the rotation of the photoconductor drive motor 1007 can be synchronized. .

[Third Embodiment] In the first embodiment, as a method of synchronizing the photosensitive drum and the scanner motor, the phase of the main scanning start signal is changed to the phase of the subscanning start signal every time the subscanning start signal is generated. The same effect can be obtained by combining them. That is, the main scanning start signal (B) obtained while the photosensitive drum and the intermediate transfer member make one rotation.
D signal) and the number of main-scanning recording line signals synchronized therewith are not limited to integers, and positioning can be performed. Hereinafter, the embodiment will be described.

FIG. 12 is a diagram showing a configuration of an image forming apparatus according to a third embodiment of the present invention, and corresponds to the above-described third method.

In the figure, reference numeral 1101 denotes a photosensitive member which is rotationally driven by a photosensitive member drive motor 1107 via a drive belt 1108. A PLL circuit 1109 controls the photoconductor drive motor 1107 at a constant speed based on a reference clock supplied from the oscillator 1114. 1115 is ITOP
With the sensor, the sensor flag 1116 shields the ITOP sensor 1115 from light each time the photoconductor 1101 makes one rotation, thereby generating an ITOP signal. Based on the ITOP signal, the writing position of the first line of the photosensitive member 1101 is determined.

Reference numeral 1112 denotes a phase matching circuit.
3 generates the reference clock generated by the ITOP sensor 11
15 is phase-synchronized with the ITOP signal generated by the reference numeral 15.
Reference numeral 1110 denotes a PLL circuit which controls the low-speed rotation of the scanner motor 1102 based on the reference clock phase-synchronized with the ITOP signal by the phase matching circuit 1112.

As described above, the phase of the ITOP signal and the reference clock are matched by the phase matching circuit 1112, whereby the rotational phase of the scanner motor 1102 is always corrected to be the same for each ITOP signal. Therefore, the rotation phase of the polygon mirror 1103 driven by the scanner motor 1102 is synchronized with the ITOP signal, and the position where the laser beam emitted from the laser 1104 is line-scanned on the surface of the photoconductor 1101 via the lens 1105 is determined. They always match on the basis of the ITOP signal.

FIG. 13 is a diagram for explaining the relationship between the actual main scanning line on the photosensitive member shown in FIG. 12 and the ITOP signal.

As shown in FIG. 13, the photosensitive member 1601 has n
The configuration is such that one rotation is made in the main scanning line of +1/2 line. Reference numeral 1602 denotes an ITOP sensor.
A sub-scanning start signal (ITOP signal) is generated at a predetermined position every one rotation.

In the image forming apparatus having the above-described structure, the photosensitive member 1601 makes one rotation while n + 1 /
Since two main scanning lines are generated, the first line of the first rotation and the first line of the second rotation are generated as shown in FIG.
The line is shifted by a half line of a fraction.

However, the rotation phase of the scanner motor 1102 for driving the main scanning line every time the ITOP signal is generated by the phase matching circuit 1112 as shown in FIG.
By synchronizing with the P signal, the scanning position of the first line for each ITOP signal can be adjusted as shown in FIG.

Hereinafter, the configuration of a data processing program readable by the image forming apparatus according to the present invention will be described with reference to a memory map shown in FIG.

FIG. 14 is a view for explaining a memory map of a storage medium for storing various data processing programs readable by the image forming apparatus according to the present invention.

Although not shown, information for managing a group of programs stored in the storage medium, for example, version information, a creator, etc. is also stored, and information dependent on the OS or the like on the program reading side, for example, a program is stored. An icon or the like for identification display may also be stored.

Further, data dependent on various programs is also managed in the directory. In addition, a program for installing various programs on a computer or a program for decompressing a program to be installed when the program to be installed is compressed may be stored.

The functions shown in FIG. 9 in this embodiment may be performed by a host computer by a program installed from the outside. In this case, the present invention is applied even when a group of information including a program is supplied to the output device from a storage medium such as a CD-ROM, a flash memory, or an FD, or from an external storage medium via a network. Things.

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 supplied.
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.

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

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the 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.

[0166]

As described above, the first embodiment according to the present invention is described.
According to the tenth aspect, the phase difference between the sub-scanning start signal generated in synchronization with the rotation of the image carrier and the main scanning start signal generated by detecting the scanned light beam is detected, Since the output timing of the sub-scanning start signal is delayed and adjusted based on the detection result, the sub-scanning start signal is always adjusted to the center of the cycle of the main scanning start signal regardless of the timing at which the sub-scanning start signal is generated. Even when the phase difference between the sub-scanning start signal and the main scanning start signal slightly fluctuates, the read or write timing of the memory in which the image data is to be stored is not shifted for each color on the recording medium. This makes it possible to obtain a high-quality color image with no color shift by matching the writing start position of the image of each color with the position of the first color.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to a first exemplary embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a printer unit of the image forming apparatus illustrated in FIG.

FIG. 3 is a timing chart illustrating image forming timing of a printer unit of the image forming apparatus illustrated in FIG. 1;

FIG. 4 is a block diagram illustrating a configuration of an image memory in the image forming apparatus according to the present invention.

FIG. 5 is a block diagram for explaining a configuration of phase adjustment control in the image forming apparatus according to the present invention.

FIG. 6 is a diagram illustrating a correspondence relationship between an image forming position of the photosensitive drum illustrated in FIG. 5 and a main scanning synchronization signal.

FIG. 7 is a circuit diagram illustrating a configuration of a phase matching circuit illustrated in FIG. 2;

FIG. 8 is a timing chart illustrating the operation of the phase matching circuit shown in FIG. 7;

FIG. 9 is a flowchart illustrating a phase matching processing procedure of the image forming apparatus according to the first exemplary embodiment of the present invention.

FIG. 10 is a timing chart illustrating a phase matching process of the image forming apparatus according to the second exemplary embodiment of the present invention.

FIG. 11 is a diagram illustrating a configuration of an image forming apparatus according to a second embodiment of the present invention.

FIG. 12 is a diagram illustrating a configuration of an image forming apparatus according to a third embodiment of the present invention.

13 is a diagram for explaining the relationship between an actual main scanning line on the photosensitive drum shown in FIG. 12 and an ITOP signal;

FIG. 14 is a diagram illustrating a memory map of a storage medium that stores various data processing programs that can be read by the image forming apparatus according to the present invention.

FIG. 15 is a diagram illustrating a state of a sub-scanning start signal generation position in a conventional image forming apparatus.

FIG. 16 is a diagram illustrating a configuration of motor drive control in a conventional image forming apparatus.

FIG. 17 is a timing chart showing a main scanning synchronization signal, an ITOP signal of a first color and a second color, read data, write data, and a timing of scanning of an optical system in a conventional image forming apparatus.

FIG. 18 is a timing chart showing a main scanning synchronization signal, an ITOP signal of a first color and a second color, read data, write data, and a timing of scanning of an optical system in a conventional image forming apparatus.

FIG. 19 is a diagram illustrating an operation of capturing CCD line data in a conventional image forming apparatus.

FIG. 20 is a diagram illustrating image forming timings in a main scanning direction and a sub-scanning direction in a conventional image forming apparatus.

FIG. 21 is a diagram illustrating a relationship between a phase relationship between a main scanning synchronization signal, a writing main scanning synchronization signal, and a sub-scanning synchronization signal and a relationship between memory contents in a conventional image forming apparatus.

[Explanation of symbols]

 101 Image writing timing control circuit 103 Polygon mirror 107 BD sensor 110 ITOP sensor 122 Phase matching circuit 130 CPU

Continued on the front page F term (reference) 2C262 AA05 AA17 AA24 AA26 AA27 AB15 AC02 AC04 FA03 FA06 GA04 2C362 BB37 BB50 CA22 2H027 DE02 EE02 EE06 2H030 AA01 AD17 9A001 BB04 BB06 DD15 HH31 JJ35 KK42 KK54

Claims (12)

[Claims] 1. An image forming apparatus for forming a multicolor image by sequentially superimposing images for each color component based on document image information to be read, a reading device for reading a document image, and a document image read by the reading device A memory for storing information; a sub-scanning start signal output means for generating a sub-scanning start signal in synchronization with the rotation of the driven image carrier; and a light beam modulated based on image information for each color component Scanning means for deflecting the light beam to scan on the image carrier rotated and driven by the driving means; main scanning start signal output means for detecting the scanned light beam to generate a main scanning start signal; A phase difference between the sub-scanning start signal and the main scanning start signal when writing or reading original image information in the memory in synchronization with the scanning start signal and the main scanning starting signal; And a delay unit for delaying the sub-scanning start signal by a predetermined time based on the following. 2. The image forming apparatus according to claim 1, wherein the delay unit delays the sub-scanning start signal so that the sub-scanning start signal is aligned with the center of the main scanning start signal cycle. 3. The sub-scanning start signal according to claim 1, wherein the delay unit delays the sub-scanning start signal so that the sub-scanning start signal at the predetermined timing coincides with a predetermined area in a main scanning start signal cycle. Item 2. The image forming apparatus according to Item 1. 4. A predetermined area within the main scanning start signal cycle is an area centered on a main scanning start signal cycle center corresponding to a phase variation between a main scanning start signal and a sub-scanning start signal. The image forming apparatus according to claim 3, wherein: 5. The image forming apparatus according to claim 1, wherein the sub-scanning start signal output unit outputs the sub-scanning start signal twice each time the image carrier makes one rotation. 6. An image forming apparatus for forming a multicolor image by sequentially superimposing images for each color component based on document image information to be read, a reading device for reading the document image, and a document image read by the reading device A memory for storing information; a driving unit for driving the image carrier to rotate; a sub-scanning start signal output unit for generating a sub-scanning start signal in synchronization with the rotation of the image carrier driven by the driving unit; Scanning means for deflecting a light beam modulated based on the image information for each color component to scan on an image carrier rotated and driven by the driving means; and detecting the scanned light beam for main scanning Main-scanning start signal output means for generating a start signal; and writing and reading original image information in and from the memory in synchronization with the sub-scanning start signal and the main scanning start signal. , On the basis of the phase difference between the sub-scanning start signal and the main scanning start signal, the image forming apparatus characterized by having a delay means for delaying the sub-scanning start signal for a predetermined time. 7. A reading device for reading a document image, and a memory for storing document image information read by the reading device, wherein a plurality of images for each color component are sequentially superimposed based on the read document image information. An image forming control method in an image forming apparatus for forming a color image, comprising: a sub-scanning start method for generating a sub-scanning start signal in synchronization with rotation of the image carrier driven by driving means for rotating the image carrier. A signal output step, deflecting the light beam modulated based on the image information for each color component, scans the image carrier that is rotationally driven by the driving unit, and detects the scanned light beam. A main-scanning start signal output step of generating a main-scanning start signal; and writing or reading of document image information in the memory in synchronization with the sub-scanning start signal and the main scanning start signal. A delaying step of delaying the sub-scanning start signal by a predetermined time based on a phase difference between the sub-scanning start signal and the main scanning start signal. 8. The image forming control method according to claim 7, wherein the delaying step delays the sub-scanning start signal so that the sub-scanning start signal is aligned with the center of the main scanning start signal cycle. 9. The method according to claim 1, wherein the delaying step delays the sub-scanning start signal so that the sub-scanning start signal at the predetermined timing is adjusted to a predetermined area in a main scanning start signal cycle. Item 8. The image forming control method according to Item 7. 10. A predetermined area within the main scanning start signal cycle is an area centered on a main scanning start signal cycle center corresponding to a phase variation between a main scanning start signal and a sub-scanning start signal. The image forming control method according to claim 9, wherein: 11. The image forming control method according to claim 7, wherein in the sub-scanning start signal output step, the sub-scanning start signal is output twice each time the image carrier makes one rotation. 12. An image forming control method in an image forming apparatus for forming a multicolor image by sequentially superimposing images for each color component based on document image information to be read, comprising: a reading step of reading a document image; A storage step of storing document image information read in the reading step in a memory; a driving step of rotating the image carrier; and a sub-scanning start signal in synchronization with the rotation of the image carrier driven in the driving step. A sub-scanning start signal output step to be generated; a scanning step of deflecting a light beam modulated based on image information for each color component to scan on an image carrier that is rotated and driven by the driving step; A main scanning start signal output step of detecting a light beam to be transmitted and generating a main scanning start signal; and an original image in the memory in synchronization with the sub-scanning start signal and the main scanning start signal. A delay step of delaying the sub-scanning start signal by a predetermined time based on a phase difference between the sub-scanning start signal and the main scanning start signal when writing and reading information. Formation control method.