JP3399350B2 - Image forming device - Google Patents

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 using a so-called tandem system.

[0002]

2. Description of the Related Art As an image forming apparatus for performing color printing,
For example, a so-called tandem system in which an image forming unit that prints yellow (Y), magenta (M), cyan (C), and black (BK) is provided and printing is performed on each sheet by sequentially printing each color is performed. Image forming apparatuses are known. In this type of image forming apparatus, yellow (Y), magenta (M), cyan (C), and black (BK) toners are sequentially transferred onto a sheet to form a color image, so that an image forming unit for each color is provided. Position accuracy is important. That is, if the arrangement accuracy of the image forming units for each color is poor,
The formed image is misaligned, resulting in an image with poor print quality.

For this reason, conventionally, the circuit shown in FIG. 19 is used in order to prevent the positional deviation of the image for each color and to obtain an image of excellent print quality. This circuit writes the print data input via the input control unit 70 into the line buffer 71, and when the address control unit 72 reads the data from the line buffer 71, the data is selected and read to correct the print data and output. The corrected print data is output to a print head (not shown) via the control unit 73.

20 to 23 are diagrams for explaining the writing and reading processes of the print data to and from the line buffer 71. The seven line buffers 1 to 7 shown in FIG. 19 are each divided into three in the main scanning direction, and each line has data for three divided lines of 1/3 to 3/3.
Further, FIG. 20 shows a state in which data is written in the line buffers 1 to 6.

This state indicates a state in which the data write processing to the line buffers 1 to 6 has been completed, and the data of the halftone line processing shown in the figure is read from this memory state. This data is data of "1", "1", ... "5", and is used as correction data of print data by the image forming unit having a positional deviation.

After the above processing, as shown in FIG. 21, the 7th line (7-1 / 3 to 3/3) of the line buffer 70.
New print data is written in the sections "1" to "6". Then, the read process of the print data of the sixth line is performed. This reading process also corresponds to the image forming unit having the positional deviation, and for example, a straight line can be printed by performing the printing process according to this data.

Similarly, as shown in FIGS. 22 and 23, the correction data is created while the print data of the seventh line is read out, and the print processing is performed.

[0008]

In the conventional image forming apparatus, the line buffer 70 has a large capacity as described above. That is, in the above example, after all the print data of the sixth line is written, the read process of the print data including the data of the sixth line is performed. Therefore, when the line capacity for 6 lines is required for the correction of the print data, a line buffer (memory) in which the print data of 7 lines can be written is required.

On the other hand, even when the positional deviation occurs, the positional deviation may be large or small. For example, when the positional deviation is small, it is not necessary to perform the correction process corresponding to the large positional deviation.

The present invention has been made in view of the above circumstances, and makes it possible to use a memory having a small capacity while changing the correction method depending on whether the positional deviation of the image forming unit is large or small. An image forming apparatus for performing a correction process of print data is provided.

[0011]

According to the present invention, the above object is to provide an image carrier that moves in the sub-scanning direction, and
Multiple recording elements lined up in the main scanning direction
Multiple arranged in different positions image forming unit comprising a print head for performing more image recorded on the image bearing member along the sub-scanning direction
Each printhead is compatible with the different colors it produces.
In an image forming apparatus that performs multicolor recording by superimposing images on the same recording medium , based on print information input from a higher-level device.
The corresponding image data to be printed is generated for each color.
A plurality of image data generating means and one line of image data
Data density conversion means for generating line-divided image data
For temporarily storing the divided image data for a plurality of lines.
Buffer memory means, and a main scanning direction and a sub-scanning direction orthogonal to each other
The divided image data is based on the two-dimensional spatial coordinates based on the orientation.
Write address into the buffer memory in sequence.
Recording between the image designating unit including the print designation unit and the print head
A correction value memory that stores the correction value corresponding to the amount of positional deviation.
And the recording positions of other image forming units based on the correction value.
Divided image data stored in the storage area where misregistration is corrected
Data is sequentially addressed and read from the buffer memory.
Read-out address designating means and the size of the correction value
Address specified by the read address designating means according to
Switching means for switching the rate of change of the dress value,
Line data read according to the addressing means
To the print head to drive the print head for each color.
This can be achieved by providing an image forming apparatus that includes a print control unit that moves and performs recording control .

That is, in this example, data of a plurality of lines at different writing times are stored in the buffer memory,
When there is a parallelism deviation between the print heads, the writing area of the line data to be written in the buffer memory is switched by the switching means according to the deviation amount. With this configuration, it is possible to perform the position correction that matches the case where the arrangement deviation of the image forming unit is large and the case where the deviation is small.

According to a second aspect of the present invention, in the first aspect of the invention, the print head is composed of, for example, a fixed type array-shaped writing element. The third aspect is the invention according to the first or second aspect, in which each print head is
Form mark images at different positions on the image carrier of each color.
The mark image forming means to be formed and the respective image carriers are opposed to each other.
And a detection means provided for detecting the mark image, and the detection means.
Markers formed by each print head detected by the output means.
Each print head or image formation based on the image detection time
The correction value corresponding to the displacement position of the unit is
And a storage unit for writing in the storage unit.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. <First Embodiment> FIG. 2 is an overall configuration diagram of an image forming apparatus according to the present embodiment. The image forming apparatus used in the description of this embodiment is a so-called tandem type color printer. In the figure, the color printer 1
Is composed of a paper supply / conveyance mechanism 2, a plurality of image forming units 3, and a fixing device 4. Paper supply / transport mechanism 2
Is composed of a sheet feeding cassette 5 in which sheets P are stacked and stored, and a sheet conveying system 6. Further, the paper transport system 6 supplies a paper feed roller 8 for carrying out the paper P from the paper feed cassette 5, a paper transport path 7 for carrying the paper P carried out by the paper feed roller 8, and a paper position in conformity with the toner image. It is composed of a standby roll 9 for feeding and feeding paper, drive rolls 10 and 11 driven by a motor (not shown), and a conveyor belt 12 rotated by the drive rolls 10 and 11.

The sheet P conveyed from the sheet feeding cassette 5 to the sheet conveying path 7 by the rotation of the sheet feeding roller 8 is sent to the standby roll 9 by the rotation of the sheet feeding roller 8 and is formed on the photosensitive drum described later. It moves on the conveyor belt 12 at a timing that coincides with the formed toner image.

While the paper P is moving on the conveyor belt 12, the paper P on the conveyor belt 12 is attached to each image forming unit 15,
The toner of each color is transferred by 16, 17, and 18, and the color transfer is performed on the paper P. After that, heat fixing processing is performed by the fixing device 4, and the paper P is carried out of the machine.

The fixing device 4 is composed of a heat roll 4a and a pressure contact roll 4b. While the paper P is nipped and conveyed between the heat roll 4a and the pressure contact roll 4b, for example, a plurality of colors of color transferred onto the paper P are transferred. The toner is melted and printed on the paper P.

On the other hand, the image forming unit section 3 is, as described above, yellow (Y), magenta (M), cyan (C),
Four black (BK) image forming units 15-18
And are arranged in this order. Yellow (Y), magenta (M), and cyan (C) are image forming units 15 to 17 that perform color printing by subtractive color mixing, and a black (BK) image forming unit 18 is an image forming unit used for monochrome printing. Is.

The image forming units 15 to 18 have exactly the same structure except for the developer (color) stored in the developing container, and a charging device, a print head, and a charging head near the peripheral surface of the photosensitive drum.
The developing device and the transferring device are arranged in this order. Where 4
The image forming unit 15 for yellow will be described as an example of the individual image forming units 15 to 18 to describe the configuration. The peripheral surface of the photoconductor drum 20 is made of, for example, an organic photoconductive material, and in the vicinity of the peripheral surface of the photoconductor drum 20, a charger 21, a print head 22, a developing roll 23 ′ (developing device 2
3), a transfer device (not shown) is sequentially arranged. The photoconductor drum 20 rotates in the direction of the arrow, and first, by applying an electric charge from the charger 21, the peripheral surface of the photoconductor drum 20 is uniformly charged. Next, an electrostatic latent image is formed on the peripheral surface of the photoconductor drum 20 by optical writing based on the print information from the print head 22, and a toner image is formed by the developing process by the developing roll 23 '. At this time, the toner image formed on the peripheral surface of the photosensitive drum 20 is formed by the yellow (Y) color toner contained in the developing container 23. The toner image thus formed on the peripheral surface of the photoconductor drum 20 reaches the position of the transfer device as the photoconductor drum 20 rotates in the direction of the arrow, and is transferred on the transfer belt 12 by the transfer device. It is transferred to the paper P.

The toner image transferred onto the upper surface of the paper P is conveyed in the direction of the arrow along with the movement of the conveyor belt 12, and the other image forming units 16 and 17 having the same construction as described above produce yellow (Y) color. The toners of magenta (M) and cyan (C) are sequentially transferred together with the toner,
Color printing is performed by subtractive color mixing. For example, if the printed image is blue, the magenta (M) color toner is transferred from the image forming unit 16 to the paper P based on the principle of subtractive color mixing, and then the cyan (C) color toner is supplied from the image forming unit 17 to the paper. Transfer to P and realize a blue image. Also,
For example, if the print image is red, the yellow (Y) color toner is transferred from the developing unit 15 to the paper P, and then the magenta (M) color toner is transferred to the paper P from the image forming unit 16 to obtain the red image. To realize.

On the other hand, the image forming apparatus 1 of this example is provided with eight photosensors 24Y, 24M, 24C, 24BK and 24Y ', 24M', 24C ', 24BK'. The photo sensors 24Y ', 24M', 24
C ′ and 24BK ′ are photosensors 24Y and 24Y shown in FIG.
It is in a state where it cannot be displayed because it is hidden by the shadows of 24M, 24C and 24BK. These photo sensors 24Y, 24M, 24
C, 24BK, and 24Y ', 24M', 24C ', 2
4BK 'corresponds to the corresponding image forming unit 15 to
18 is a sensor for detecting marks (line-shaped marks) provided on the photoconductor drum 20, and, for example, photosensors 24Y and 24Y ′ detect marks on the photoconductor drum 20 provided on the image forming unit 15, Photo sensor 2
4M and 24M 'detect the mark on the photoconductor drum 20 provided in the image forming unit 16, and the photosensor 24C
And 24C 'detect the mark on the photoconductor drum 20 provided in the image forming unit 17, and the photosensor 24BK,
24 BK ′ detects a mark on the photosensitive drum 20 provided in the image forming unit 18.

FIG. 1 (a) is a perspective view for explaining the above structure. It should be noted that FIG. 4A shows four image forming units 15
Among them, a perspective view of the vicinity of the image forming unit 15 is shown as a typical example. As described above, the image forming unit 15
Is composed of the photosensitive drum 20, the print head 22, etc.,
The photosensitive drum 20 is exposed from the print head 22 through the SELFOC lens 26 based on the image data,
A line-shaped electrostatic latent image 27 is formed. This electrostatic latent image 2
7 is visualized by the developing roll 23 'and becomes a toner image (mark 28). The above-mentioned photosensors 24Y, 2
4Y 'is located on the side part which is off the transfer roll (not shown),
The configuration is such that the mark formed on the photoconductor drum 20 can be detected. Further, the photosensors 24Y and 24Y 'detect the ends of the line-shaped marks 28 at the corresponding positions.
Note that FIG. 3 is an enlarged view of the part marked with a circle in FIG.

On the other hand, FIG. 1B illustrates an example of detecting the θ deviation particularly in the case of the above arrangement example. First, if the photoconductor drum 20, the print head 22, etc. are mounted in parallel, the line-shaped marks 28 formed on the photoconductor drum 20 are parallel, and the photosensors 24Y on both sides,
There is no time lag in detecting the mark 28 by 24Y '. However, if the photoconductor drum 20 and the print head 22 are not mounted in parallel, naturally both photosensors 2
There is a deviation in the time when 4Y and 24Y 'detect the mark 28.

For example, the mark 28 on the photosensor 24Y side from the home position (position of 0 ° in FIG. 1B).
If the detection time of the same mark 28 on the photosensor 24Y ′ side is longer than Δt1 by Δt when the detection time of Δt is t1, for example, a positional deviation occurs by the length of the photosensitive drum 20 moving by Δt. Will be there.

In this example, before the actual printing process, the line-shaped mark 28 is formed, the amount of displacement (θ displacement) between the print heads is detected in advance, and the amount is written in the EEPROM described later. . With this configuration, the θ deviation correction is performed based on the correction data written in the EEPROM during the actual printing process.

In this example, twelve marks 28 described above are formed on the peripheral surface of the photoconductor drum 20, and as shown in FIG.
Perform 12 times while 0 rotates once. On the other hand, FIG. 5 shows a circuit configuration of the color printer 1 having the above configuration. The color printer 1 includes an interface control unit (I / F control unit) 29.
And an engine control unit 39. Further, the engine control unit 39 includes a CPU 30, a ROM
31, a RAM 32, an EEPROM 33, a head drive control unit 34, an input / output control unit 35, and a color engine unit 36. The CPU 30 controls the entire system of the color printer 1 according to the present embodiment, and controls according to the program stored in the ROM 31. In addition, RAM32
Stores data generated during the control processing of the CPU 30.
An operation panel 38 is also connected to the CPU 30, and a key operation signal is sent from the operation panel 38 to the CP.
Supplied to U30.

On the other hand, the EEPROM 33 stores correction data for printing, which will be described later. This correction data is the measurement result described with reference to FIGS. 1A and 1B described above, and is data for performing θ deviation correction. This correction data is used during processing by the head drive control unit 34.

FIG. 6 is a diagram for explaining the circuit configuration of the head drive controller 34 described above. The head drive controller 34 includes an input controller 50, a memory 51, an output controller 52, and an address controller 53. The address control unit 53 is composed of an address output unit 54 and an address processing unit 55, and the address processing unit 55 has a -1/3 line output unit 56.
a, -3/3 line output unit 56b, multiplexer 5
7, a read line correction counter 58, a 1/3 line update counter 59, an adder 60, and a multiplexer 61.

The multiplexer 61 is a selection circuit that selects a write address when reading data from the memory 51 via the input control unit 50 and a read address when reading data from the memory 51. The multiplexer 57 is a circuit that selects either the above-mentioned −1/3 line output unit 56a or −3/3 line output unit 56b, and depending on the magnitude of the positional deviation described later (depending on the magnitude of the correction data), This is a circuit that selects either output unit 56a or 56b. The adder 60 is a counter that adds the output of the multiplexer 57, the output of the read line correction counter 58, and the output of the 1/3 line update counter 59.

On the other hand, returning to the description of FIG. 5, the printer engine 36 transfers the image data of yellow (Y), magenta (M), cyan (C), and black (BK) to the corresponding print head 22 (hereinafter, yellow (Y The print head disposed in the Y) image forming unit 15 is indicated by 22Y, the print head disposed in the magenta (M) image forming unit 16 is indicated by 22M, and the cyan (C) image forming unit 17 is indicated.
22C shows the print head arranged on the black (B
K) has a drive circuit for outputting the print head disposed in the image forming unit 18 to 22BK), and FIG. 7 shows a specific circuit example. 7 shows, for example, the print head 2
2 shows an example of 2Y.

As shown in the figure, the print head (for example,
Yellow (Y) is composed of a shift register 45, a latch circuit 46, a NAND gate (NAND gate) 47, and a driving transistor 48, and controls lighting of the LED element 49 according to a signal output from the driving transistor 48. The shift register 45 has a configuration capable of serially inputting video data for one line, and uses a clock signal (CL
Print data (HDATA) for one line in synchronization with K)
Enter. The latch circuit 46 is a circuit for latching the video data input to the shift register 45 in synchronization with the latch signal (LATCH), and the print data latched in the latch circuit 46 is output to the NAND gate 47 in synchronization with the strobe signal (STROB). To be done.

The print data output to the NAND gate 47 is, for example, a high (H) signal only for dots to be printed, and a high (H) or low (L) signal is output from the corresponding output of the NAND gate 47 to the drive transistor 48. Then, the corresponding LED element 49 is driven. The above-described configuration is the same for the other print heads 22M, 22C, 22BK of magenta (M), cyan (C), and black (BK), and the print head 22 is based on the respective video data.
Optical writing is performed from the (LED element 49) to the photosensitive drum 20.

The exchange of signals between the PPC color engine section 36 and the CPU 30 other than the above-mentioned video data is carried out under the control of the above-mentioned input / output control section 35. The processing operation of the color printer 1 having the above configuration will be described below.

As described above, each image forming unit 15-
18 includes photosensors 24Y to 24BK and 24Y '.
~ 24BK 'are provided, and these photosensors 24Y are provided.
~ 24BK, 24Y '~ 24BK' is the conveyor belt 12
It is provided at a position beyond the belt width of.

First, the correction data is measured in order to detect the amount of displacement of the image forming unit 15 and the like. This correction data is created at the so-called warm-up after turning on the power of the color printer device 1 of this example, or when the image forming unit is replaced. As described above, each photosensitive drum 2
Twelve marks are printed at 0. For example, as shown in FIG. 4 described above, the exposure output from the print head 22 is performed 12 times during one rotation of the photosensitive drum 20.

Therefore, an electrostatic latent image is formed on the photosensitive drum 20 by sequentially exposing 12 times from the print head 22, and the mark is visualized by the developing process by the developing roll 23 ', and the photosensors 24Y and 24Y are formed. Read sequentially by '. FIG. 8 is a diagram in which the data read as described above is plotted over time.
Here, for example, if the image forming unit 15 has no eccentricity, the mark detection time interval is constant (for example, a constant time t).
Should be 0). That is, the photo sensor 24Y
This is because the position is fixed, and the mark detection time interval becomes constant if the photosensitive drum 20 rotates at a constant speed without eccentricity.

However, the mark detection time interval having a periodic curve as shown in FIG. 8 indicates that the photosensitive drum 20 (image forming unit 22Y) has an eccentricity. In addition, the above-described detection processing is performed by the other photo sensor 24.
This is also performed on the Y ′ side, and the θ deviation amount described with reference to FIG. 1B above is detected from the measurement results by both photosensors 24Y and 24Y ′. In this example, this data is stored in the EEPROM 3
The data is written in No. 3, and is used as correction data in the subsequent print processing.

Next, the printing operation in the actual printing process will be described. Print data supplied from a host computer such as a personal computer is supplied via the I / F control unit 29 and stored in the RAM 32 under the control of the CPU 30.

Next, the CPU 30 outputs the print data stored in the RAM 32 to the head drive controller 34, and the EEPR
The print data is corrected according to the correction data stored in the OM 33. 9 to 12 are diagrams for explaining the above-mentioned correction processing.

First, in FIG. 9, it is assumed that the print data output from the RAM 32 is written in the memory 51 in a range surrounded by a dashed line in FIG. Ie 1
The print data for 5 lines of the page is written, and one dot line in the main scanning direction is composed of 3 lines of 1/3 to 3/3. The first line of the first dot is 1-
1/3, the second line of the first dot is 1-2 / 3
, The third line of the first dot is 1-3 / 3, the first line of the second dot is 2-1 / 3, and the second line of the second dot is 2- / 3. 2/3, 2
The third line of the dot is 2-3 / 3.

With the above-mentioned print data expanded in the memory 51, the print data is then written in the memory 51. The writing of the next print data is the data of the sections "1" to "6" of the sixth line shown in FIG. 9 (enclosed by a two-dot chain line in FIG. 9). The write (write) process of the print data is performed by the write address output from the address output unit 54. The write address is composed of a main scanning direction designation address for designating an address in the main scanning direction and a sub scanning direction designation address for designating an address in the sub scanning direction. Regarding the position in the main scanning direction, the sixth line (1/3 to 3). The address of / 3) is designated, and the address data designating the sections "1" to "6" for the line is output. When the multiplexer 61 performs the write process,
The write address is selected, and the data is written in the area designated by the addresses in the main scanning direction and the sub scanning direction.

Next, read processing is performed. 9 is a memory position where data is read from the memory 51. This data read process (read process) is performed by a read address. This read address is also composed of a main scanning direction designation address and a sub scanning direction designation address, and the main scanning direction designation address is 1
A signal for updating the line by 1/3 is output from the / 3 line update counter 59 to the adder 60. A correction count signal is also output from the lead line correction counter 58, and the adder 60 sequentially updates the initial value in the main scanning direction by 1/3 in accordance with both signals. It should be noted that the update processing for every 1/3 in the main scanning direction is actually −
1/3 addition processing, that is, 1/3 subtraction processing. On the other hand, the intervals are sequentially subtracted along with the above processing. By outputting such a read address, the dot data subjected to the halftone processing shown in FIG. 9 is sequentially read.

That is, when the shift amount is large, the multiplexer 57 reads the data from the -1/3 line output unit 56a. For example, in the case of the above-mentioned 6th line, 6- (1 /
From the calculation of 3), the initial value of data read is 5-3 /
This is the third line. Therefore, the address data of FIG. 9 is read as an initial value, and the subtraction processing of 1/3 is performed by the adder 60 every time the interval is sequentially updated. Then, the data of the designated address is read. By processing in this way, data is read from the memory 51 and supplied to the corresponding print head 22Y via the output control unit 52. As described above, this data is data in which dots are sequentially shifted, and corrects the above-mentioned θ deviation.

Next, the state shown by the alternate long and short dash line in FIG.
In the whole state), the next print data is written in the memory 51. The writing of the next print data is the data of the sections "7" to "11" of the sixth line shown in FIG. 10 (enclosed by a chain double-dashed line in FIG. 10). The write (write) process of the print data is also performed by the write address output from the address output unit 54 in the same manner as described above.

Next, in this memory state, read processing is performed. The shaded area in FIG. 10 is the memory 5
It is a memory location from which data is read next from 1. This data read process (read process) is also performed by the read address as described above. This read address is also composed of a main scanning direction designation address and a sub scanning direction designation address, and the initial value is updated by 1/3 by the adder 60 (lines are subtracted by 1/3 each). By outputting such a read address, the shaded data shown in FIG. 10 is read obliquely, as in the above.

That is, "6", "5", "5", ...
The data “1” is sequentially read from the memory 51 and supplied to the corresponding print head 22Y via the output control unit 52. This data is also data in which the dots are sequentially displaced as described above, and corrects the above-mentioned θ deviation.

Further, in the state shown by the alternate long and short dash line in FIG. 11, the next print data is written in the memory 51. This print data write processing is data of the sections “12” to “16” of the sixth line shown in FIG. 11 (enclosed by a two-dot chain line in FIG. 11), and this print data write (write) processing is also described above. In the same manner as described above, the write address output from the address output unit 54 is used. And
In this memory state, the read processing is performed, and the shaded data (“6”, “6”, “5”, ...
.. Read out "1"). This data is also as described above,
This is data in which dots are sequentially displaced, and in this example, the above-mentioned θ deviation is corrected.

FIG. 12 shows the data to be read next,
The data of "6", "6", ... "1" is read. Therefore, by processing as above,
For example, it is possible to perform the correction corresponding to the deviation direction of the image forming unit 15 shown in FIG. 8, and the capacity of the memory 51 can be reduced by one line as compared with the above-mentioned conventional example, and the memory 51 having a small capacity is used. The deviation can be corrected.

On the other hand, a case in which the amount of deviation (θ deviation) is small from the above measurement results will be described. In this case, the θ deviation of the image forming unit 15 is small, and therefore, FIGS.
The correction process shown in is performed. That is, first, in the state shown in FIG. 13 (the data state surrounded by the alternate long and short dash line in FIG. 13), the print data indicated by the alternate long and two short dashes line is written as in the case described above. The print data write (write) process is performed by the write address output from the address output unit 54, as described above.

Next, a read process is performed in the memory state shown in FIG. 13, and the data shaded in FIG. 13 is read from the memory 51. That is, the line data of the 5-1 / 3 line subjected to the halftone processing is sequentially output.

This data is almost linear data, for example, there is no print deviation. For example, in the case of the print misregistration as shown in FIG. 8, it is used at a portion where the print misregistration is relatively small, for example, at the portions a and b shown in FIG.

That is, the above-mentioned portions a and b have relatively little print displacement, and therefore, as shown in FIGS. 14 to 16, while writing the print data, the print data is read out linearly, for example, 5-1. The line data of the / 3rd line, the line data of the 5-2 / 3 line, the line data of the 5-3 / 3 line, and the line data of the 6-1 / 3 line are sequentially output.

In this example, the multiplexer 57 is used to make 1 /
The 3-line output unit 56a is selected, the print data is read for each 1/3 line, and at a position where the print deviation is small as indicated by a and b, the multiplexer 57 performs 3/3.
The line output unit 56b is selected, print data is read out every 3/3 line, and print processing corresponding to print misalignment is performed.

In the above example, the deviation correction of the yellow (Y) image forming unit 15 has been described, but other image forming units 16 to 18 such as magenta (M), cyan (C), black (BK), etc. The deviation correction is similarly performed.

Further, in the above-mentioned example, the line mark 28 is formed and the correction data is written in the EEPROM 33 in advance. However, the deviation amount is visually judged by printing a test chart or the like, and the operator responds to this. The correction data may be written in the EEPROM 33. <Second Embodiment> Next, a second embodiment will be described.

This example describes a more specific example for realizing the above-described embodiment. Also in this example, the print data output from the host computer shown in FIG. 5 is stored in the RAM 32 via the I / F control unit 29.
Then, the print data stored in the RAM 32 is output to the head drive control unit 34 and a correction process is performed. At this time, for example, one dot of print data is converted into three dots in the sub-scanning direction for smoothing gradation expression. That is, if one dot is shown, one dot in FIG. 17A is converted into three dots in FIG. 17B.

FIG. 18 shows data obtained as a result of performing the above conversion process on 8 × 3 dots. This data composes one line described above into three divisions of 1/3 to 3/3. For example, when printing such print data, there may be a deviation in the image forming unit 15 or the like. In this case, the same processing as described above is performed to correct the print data.

That is, the photo sensor 24 as described above.
Y, 24Y ', etc. corresponding image forming units 15 to
The position deviation of 18 is detected, and the selection process is performed by the multiplexer 57 according to the degree of the position deviation.
~ Position correction is performed according to the processing shown in Figs. 12 and 13 to 16. By performing the processing as described above, the print data can be corrected by using the memory having a small capacity and the print processing can be performed.

[0059]

As described above, according to the present invention, it is possible to correct the printing position deviation by using a memory having a small capacity, reduce the cost of the apparatus, and reduce the deviation amount. The correction amount can be switched accordingly, and a wide range of angle correction can be performed on the print result of each color.

Further, gradation data such as smoothing can be efficiently corrected, and a print image without print misalignment can be realized.

[Brief description of drawings]

FIG. 1A is a perspective view of an image forming unit according to an exemplary embodiment, and FIG. 1B is a diagram illustrating an example of measuring print misalignment.

FIG. 2 is an overall configuration diagram of an image forming apparatus according to an exemplary embodiment.

FIG. 3 is a partially enlarged perspective view of FIG.

FIG. 4 is a diagram illustrating an exposure position by a print head.

FIG. 5 is a system block diagram of the apparatus.

FIG. 6 is a diagram illustrating a configuration of an address control unit.

FIG. 7 is a specific circuit diagram of a print head.

FIG. 8 is a diagram showing a measurement result of print misalignment.

FIG. 9 is a diagram showing a specific example of data written in a memory when θ deviation is large.

FIG. 10 is a diagram illustrating an example of writing data to and reading data from a memory when the θ deviation is large.

FIG. 11 is a diagram illustrating an example of writing data to and reading data from a memory when the θ deviation is large.

FIG. 12 is a diagram illustrating an example of writing data to and reading data from a memory when the θ deviation is large.

FIG. 13 is a diagram showing a specific example of data written in a memory when the θ shift is small.

FIG. 14 is a diagram illustrating an example of writing data to and reading data from a memory when θ deviation is small.

FIG. 15 is a diagram illustrating an example of writing data to and reading data from a memory when θ deviation is small.

FIG. 16 is a diagram illustrating an example of writing data to and reading data from a memory when θ deviation is small.

FIG. 17 is a diagram illustrating an example in which one dot is divided into three in the sub-scanning direction.

FIG. 18 is a diagram illustrating an example in which 8 × 3 dot data is divided into three in the sub-scanning direction.

FIG. 19 is a diagram illustrating a conventional print data correction method.

FIG. 20 is a diagram showing a specific example of data written in a conventional memory.

FIG. 21 is a diagram illustrating an example of writing data to and reading data from a conventional memory.

FIG. 22 is a diagram illustrating an example of writing data to and reading data from a conventional memory.

FIG. 23 is a diagram illustrating an example of writing data to and reading data from a conventional memory.

[Explanation of symbols]

1 color printer 2 Paper supply / transport mechanism 3 Image forming unit 4 fixing device 5 paper cassettes 6 Paper transport system 7 Paper transport path 8 paper feed rollers 9 Standby roll 10, 11 drive roll 12 Conveyor belt 15-18 Image forming unit 20 photoconductor drum 21 Charger 22 Print head 23 Developer 23 'developing roll 24Y, 24M, 24C, 24BK Photo sensor 28 line-shaped electrostatic latent image 29 I / F controller 30 CPU 31 ROM 32 RAM 33 EEPROM 34 Head drive controller 35 I / O controller 36 Color engine section 39 I / F control unit 50 Input control unit 51 memory 52 Output control unit 53 Address controller 54 Address output section 55 Address processing unit 56a-1 / 3 line output section 56b-3 / 3 line output section 57 multiplexer 58 Lead line correction counter 59 1/3 line update counter 60 adder 61 Multiplexer

(72) Inventor Toshio Nagasaka 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Electronics Co., Ltd. (72) Toshihiko Numazu 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Electronics Co., Ltd. (56) References JP-A-8-258328 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/525 B41J 2/44 B41J 2/45 B41J 2/455

Claims (3)

(57) [Claims] 1. An image carrier moving in the sub-scanning direction, and the sub-scanning
Multiple lines arranged in a line in the main scanning direction orthogonal to
Image forming unit comprising a print head for image recording on said image bearing member is being <br/> plurality arranged in different positions along the sub-scanning direction by the recording device, different color print heads is generated
Multicolor recording by superimposing images corresponding to
In the image forming apparatus that supports
Image data generating means for generating power image data for each color
And the divided image data of multiple lines from the image data of one line
And a buffer for temporarily storing the divided image data for a plurality of lines.
Memory means and two-dimensional with reference to the main scanning direction and the sub-scanning direction orthogonal to each other
The divided image data is stored in the buffer memo based on the spatial coordinates.
Write addressing means for sequentially writing to the memory and the amount of deviation of the recording position between the image forming units including the print head.
There is a deviation in the recording position between the correction value storage unit that stores the corresponding correction value and the other image forming unit based on the correction value.
Split image data stored in the corrected storage area
Sequential addressing and reading from the buffer memory
Read address designating means, and the read address designating according to the magnitude of the correction value.
Switching hand that switches the rate of change of the address value specified by the means
The column and the read address according to the read addressing means.
Input in-data to the print head to print for each color
An image forming apparatus comprising: a print control unit that drives a head to perform recording control . 2. The image forming apparatus according to claim 1, wherein the print head comprises a fixed type array-shaped writing element. 3. An image carrier of each color by each of the print heads.
Mark images that form mark images at different positions
The mark image is provided so as to face the image forming member and each of the image carriers.
Formed of the detecting means for emitting and each print head detected by the detecting means
Each print head or image based on the detection time of the mark image
The correction value corresponding to the positional deviation of the forming unit is
The image forming apparatus according to claim 1, further comprising a storage unit that writes the positive value in the positive value storage unit .