JPH056068A - Color image forming device - Google Patents

Abstract

(57) [Summary] A color image forming apparatus capable of recording both color image data from the color image reading optical system 10 and color image data from the memory 113, wherein color image data from the reading optical system and color from the memory are recorded. A color image forming apparatus having an input key 902 for inputting a color misregistration correction amount for each piece of image data, and performing color misregistration correction according to each.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to correction of color misregistration in a color image forming apparatus. The present invention particularly relates to correction of color misregistration due to transfer position misregistration in an apparatus capable of both copying an original image and recording image data from an external device such as a host computer.

[0002]

2. Description of the Related Art FIG. 2 shows a full-color electrophotographic copying machine as an example of the prior art.

Reference numeral 1 is a photosensitive drum, 2 is a primary charger, and 3 is a surface electrometer for measuring the surface potential of the drum. Around the photosensitive drum 1, a plurality of developing units 101M (magenta), 101C (cyan), 101Y (yellow), which use a two-component developer in which toner and carrier are mixed,
01Bk (black) is loaded and the developing device 100 equipped with a movable base 120 that is movable in the left-right direction, the transfer drum 5,
The front static eliminator 6 and the cleaning device 7 are arranged.

The optical system 10 includes a document illumination lamp 21, a first mirror 11, a second mirror 12, a third mirror 13, an imaging lens 14 and a CCD 15 having B, G and R filters.
Laser scanner unit 16, fixed mirror 17, 1
It is composed of 8. Lamp 21 and mirror 11 are mirror 1
The document on the platen glass 28 is scanned at a speed twice as fast as that of the documents 2 and 13. The reflected light of the original is CC through the lens 14.
An image is formed on D15. The original image is color-separated by a CCD 15 having B, G, and R filters, converted into an electric signal, and subjected to image processing such as A / D conversion in an image processing unit 19, and then a laser scanner unit 16 Sent to the laser driver inside. The laser light oscillated by the image signal passes through the polygon scanner and the mirrors 17 and 18 in the unit 16 to form a latent image on the photosensitive drum 1.

A fixing device 20 and a paper feeding device 30 are arranged on the right side of the copying machine, and transfer paper conveying systems 25 and 35 are arranged between each of them and the transfer drum 5.

The photosensitive drum 1 has a primary charger 2 for each of four developing colors M (magenta), C (cyan), Y (yellow), and Bk (black) for each process of charging, exposing, developing, transferring, and cleaning. , The optical system 10, the developing device 100, the transfer drum 5, and the cleaning device 7.

The transfer drum 5 is gripped by the tip gripper 5a of the transfer paper P that is fed from the transfer paper cassette 31 or 32 of the paper feeding device 30 through the transport system 35, and is attracted inside the transfer drum 5. The transfer sheet P is attracted to the transfer sheet 5b by the charger 4, and is rotationally transferred so as to transfer the developed image on the photosensitive drum 1 for each developing color. A transfer charger 5c is arranged in the transfer area.

The transfer paper P on which the toner images of the respective developing colors are sequentially transferred is released from the gripper 5a, separated from the transfer sheet 5b by the separation charger 8 and separation claw 8 ', and transferred to the fixing device 20 by the transport system 25. Is sent. After the toner image on the transfer paper P is fixed on the transfer paper P by the fixing device 20,
The transfer paper P is discharged onto the tray 23.

Further, not only the original image signal from the CCD 15 but also the memory image signal from the memory means 22 such as the host computer is supplied to the image processing section 19 via the video cable 24, and the memory image is printed by the electrophotographic process. It

[0010]

However, in the above-mentioned conventional example, the color shift occurs in the recorded image due to the shift of the transfer position for each developing color due to the vibration of the transfer drum and the slight deflection of the transfer sheet. There is.

An example thereof is shown in FIGS. 3 (A) and 3 (B). That is, the first-color image forming pattern 301 and the second-color image forming pattern 302 are slightly displaced from each other, which hinders accurate reproduction of the color of the fine line (A), or causes the original on the edge of the image. A color frame that does not exist is generated (B).

[0012]

SUMMARY OF THE INVENTION The present invention distinguishes between the case of original copy and the case of memory print, and provides optimum color misregistration correction means for each.

Further, the present invention provides a print output free from color misregistration even in a composite print of an original image and a memory image.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a color copying apparatus according to the present invention will be specifically described below with reference to the drawings.

(First Embodiment) This embodiment will be described with reference to the color copying apparatus shown in FIG. First, the relative position control of the sheet and the image will be described with reference to FIGS.

In FIG. 4, 1 is a photosensitive drum, 5 is a transfer drum, and P is a transfer sheet adsorbed on the transfer drum, and the two drums rotate in the directions of arrows α and β, respectively. A on the photosensitive drum 1 is a position where a latent image is formed by a laser, and B is a position where an unfixed image developed on the photosensitive drum is transferred to the paper P. When the distance from position A to position B on the photosensitive drum along its rotation direction is L _AB ,
Distance L _AB from the transfer position B to the rotation direction of the transfer drum
The upstream position is C. Naturally, L _CB = L _AB . Position C
The position upstream of the distance L _{DC is} defined as D.

FIG. 5 shows how the original is read. When the document Q on the platen glass 28 is copied, the scanning optical system (the illumination lamp 21 and the mirrors 11, 12, 13 in FIG. 2) scans the document Q a predetermined distance before the basic stop position HP (home position). It moves to the start position ST and stops once. After that, scanning is started after a predetermined time T _W from the time when the front end of the paper P on the transfer drum reaches the position D, and the scanning is accelerated to the speed V _M corresponding to the desired copy magnification M before reaching the document front end position TP. , The image from the position TP is printed from the front end of the paper P.

FIG. 8 shows a state in which the sheet is conveyed to the transfer drum, and the sequence of copying the original will be described in detail.

Distance L from suction position F to position D
_The scanning optical system starts (801) after a time T _W from the time when the leading edge of the paper P fed to the position G on the paper conveyance path having a distance L _FG equal to _FD reaches (801) and further from the suction position F to the position described above. the leading end of the sheet P to scan the original tip when it reaches the position H of the transport path of the distance L _FC equal distances L _FH to C (802). The sheet P is attracted to the transfer drum at the position F (803), but a latent image has already been formed on the photosensitive drum at that time. The transfer of the developed first color image is started from the time when the front end of the paper P reaches the transfer position B (804), and the formation of the latent image is finished when the rear end of the paper P reaches the position H. That is, the scanning optical system reaches the trailing edge of the document (805).

When the leading edge of the paper reaches the above-mentioned position D, the scanning optical system starts the timer T _W for starting the scanning of the second color, but at this point, the transfer of the image of the first color is still performed at the position B. (806). When the trailing edge of the paper P reaches the position B, the image transfer of the first color is finished (80
7).

When the leading edge of the sheet P reaches the position C, the optical system, which has already started scanning, scans the leading edge of the document for forming the image of the second color (808). The image at that time is transferred at position B (809).

After that, the paper is attracted to the transfer drum,
The states of (806) to (809) are repeated for the number of development colors required. When the leading edge of the paper P after the transfer of the final color reaches the position I, the paper is separated from the transfer drum (810). At this time, the optical system is still scanning the original for the final color.

The position where the leading edge of the sheet should be sucked is position D.
When the next sheet reaches the same state as (801), the optical system starts the optical system scanning start timer for forming the first color image of the next sheet (811).
At this time, the transfer of the final color image on the previous sheet is still performed.

When the transfer of the previous sheet is completed (812), the leading edge of the next sheet is in the same state as (802), and when the optical system starts scanning from the leading edge of the original, a part of the previous sheet is still transferred. It is adsorbed on the drum (813).

When the leading edge of the next sheet reaches the position F and suction is started, the previous sheet has not yet completed the separation, and the optical system is already forming a latent image (814). Even when the transfer of the next sheet is started, the separation of the previous sheet is not completed (815), and when the transfer is advanced to some extent, the previous sheet is completely separated from the transfer drum (816).

After this point, the state of image formation is (805)
It becomes the same as the following. Assuming a four-color full-color copy executed in the order of magenta, cyan, yellow, and black, the condition when the optical system scan start timer starts is that there is no paper on the transfer drum when the first magenta sheet is printed ( 801), the paper is already on the transfer drum in the case of cyan, yellow, and black (806), and the previous paper is being separated in the case of the second and subsequent magenta (811). Similarly, in the state at the start timing of latent image formation, there is no paper on the transfer drum when the first sheet of magenta is present (802), and the paper is already on the transfer drum when cyan, yellow, and black (808). ) In the case of magenta for the second and subsequent sheets, the previous sheet is being separated (813).

Further, in the state of transfer, the first magenta is performed while adsorbing the paper (804 to 807), 2
Magenta after the first sheet is executed while adsorbing and separating (815, 816, 805 to 807), and cyan and yellow are performed while being adsorbed on the transfer drum (809, 8).
06, 807), the black is done separately (8
09-812).

[0028] When the original copy ideal is because L _AB = L _CB if T _AB = T _CB in FIG. 4, when the leading end of the sheet on the transfer drum has reached the position C, the scanning optical system platen If the timer T _W that starts at the position D as if scanning the position TP above is determined, the positional relationship between the original and the paper should be the same for each rotation of the transfer drum.

However, in reality, since the load applied to the transfer drum varies depending on the order of development and the number of sheets as described above, the time point T _DB slightly varies with each rotation, and the variation is printed as a color shift. .

On the other hand, in the case of the memory print, it is not necessary to consider the acceleration time of the motor and the like.
It is only necessary to read the contents of the memory at the same time that the tip of C reaches the position C. In this case as well, the time T _CB slightly varies with each rotation, and the variation is printed as a color shift.

In this embodiment, the drive timing of the motor and the read timing from the memory are independently controlled for each rotation of the transfer drum.

A control block diagram is shown in FIG. 1 and will be described below. The color separation, A / D conversion, and amplification of the digital color image signals R, G, and B in the CCD unit 109 are performed by the image processing unit 1.
In 10, the toner density signal V1 is obtained through known shading correction, input masking processing, LOG conversion processing, output, and masking / UCR processing. V1 is any one of M, C, Y, and Bk depending on the development color. On the other hand, memory 1
13 stores image data sent from an external device 116 such as a host computer, image data read by a CCD, and image data generated by the CPU 101. The read / write timing and address of the memory 113 are commanded by the CPU 101 according to a command from the memory controller 11
4 is directly controlled.

One of the image V2 read from the memory 113 and the image V1 read from the image processing unit 110 is selected by the selector unit 111, and the laser 112 is driven. The selector unit 111 can switch between V1 and V2 in pixel units. The CPU 101 of the pulse motor 109 is an I / O
It is driven by the DRIVE pulse output through the unit 106, and its speed is controlled by the pulse period.

In the memory control unit 114, the CPU 101
Output of image data from the memory 113 is started in response to a START signal output via the / O unit 106.

The timer 1 is triggered by a signal VSYNC1 which will be described later and after counting a predetermined number of CPU clocks INT1
Generate a signal.

The timer 2 generates an INT2 signal after counting a predetermined number of horizontal synchronizing signals HSYNC using a signal VSYNC2 described later as a trigger. The CPU 101 starts driving the motor when the generation of the INT1 signal is detected, and starts the image output from the memory when the generation of the INT2 signal is detected.

The CPU 106 is a well-known ROM 102, RA
It has an M 103 and an I / O unit 106, and controls the operation unit 108.

Referring to FIG. 6, the above-mentioned signal VSYNC1,
The VSYNC2 will be described. (A) shows the generation position of each VSYNC signal. The signal VSYNC1 is generated when the leading edge of the paper P on the transfer drum reaches the above-mentioned position D. Signal V
SYNC2 also occurs when the leading edge of the paper P reaches the position E. The position E is located a predetermined distance upstream of the position C.

Assuming that the process speed, that is, the peripheral speed of the transfer drum is S, it takes time for the leading edge of the sheet to travel from position D to position B.

[0040]

[Outer 1] Requires. here

[0041]

[Outside 2] Indicates a variation due to the development order. That is, in the case of 4-color copy,

[0042]

[Outside 3] Is magenta,

[0043]

[Outside 4] Is cyan,

[0044]

[Outside 5] Is yellow,

[0045]

[Outside 6] Is the time when black and takes positive or negative value. Assuming that the time for the image on the photosensitive drum to travel from position A to position B is T _AB = L _AB / S, and it does not change for each development color, the leading edge of the document is scanned after (T _DBi −T _AB ) time from the occurrence of signal VSYNC1. It will be good if you do.

On the other hand, since the acceleration time T _V of the scanning optical system to the desired speed V _M is known in advance, the time from the occurrence of VSYNC1 to the start of scanning of the optical system is T _1i = (T _DBi −T _AB
−T _V ), (i = 1, ... 4).

On the other hand, similarly, the leading edge of the paper is moved from position E to position B.
Time to live

[0048]

[Outside 7] Requires. here

[0049]

[Outside 8] Also shows the variation for each development color. Therefore, T _2i = (T
_EBi- T _AB ), (i = 1, ... 4), the signal VSY
The image output from the memory may be started T _2i time after the occurrence of NC2.

[0050]

[Outside 9] Is empirically determined so as to be the center value of the variation for each developing color, and is stored in a non-volatile memory such as a RAM backed up by a battery or an electrically erasable EEPROM. Further, the acceleration time T _{V of the} motor corresponding to all the copy magnifications in the feasible range and

[0051]

[Outside 10] The VSYNC signal generation positions D and E are determined so that T _1i and T _2i take positive values.

FIG. 7 shows a control flow, which will be described below.

When the start of the copy or print operation is instructed (701), the acceleration time T _V and the distance L _V required for acceleration are also stopped from the magnification M (702). Next, the optical system is preliminarily advanced to the front of the document L _V (703). As described above, T _1i and T _2i are obtained (704). After the paper is fed (705), RA is used as a counter showing the development color.
The area i on M is set to 1 (706). In FIG. 7, since four full colors are handled, 1 is magenta, 2 is cyan,
3 means yellow and 4 means black.

When the occurrence of the signal VSYNC1 is detected (7
07), the time T _1i is set to the timer 1 (7)
08). When the occurrence of the signal VSYNC2 is detected (70
9), set the time T _2i in the timer 2 (71)
0). When the count-up signal INT1 of the timer 1 is detected (714), the motor is driven to start the forward movement of the optical system (715), and the count-up signal I of the timer 2 is started.
When NT2 is detected (716), STA is sent to the memory controller.
The RT signal is output (718) and the output of the memory image is started. When the above process is completed, the counter i is incremented (722) and the process proceeds to step 707 to control the second color.

When the control for four colors is completed, the counter i is cleared to 0 (720), and the process proceeds to step 705 for printing the second sheet. After printing the specified number of sheets, exit the flow.

Although omitted from the flow, the scanning optical system returns to the scanning start position again when the trailing edge of the original is reached.
The optical system does not scan during memory printing.

In FIG.

[0058]

[Outside 11] An example of the adjustment operation is shown. Reference numeral 900 denotes a part of an operation unit of the color copying machine according to the present embodiment, 901 is a liquid crystal display unit having a dot matrix configuration, and 902 is for changing data displayed on the liquid crystal display unit and selecting a desired mode. Is a group of keys used for. FIG. 9 shows an example of a screen for setting data for color misregistration adjustment for each color by distinguishing between original copy and memory print. Cursor display with ↑ and ↓ keys

[0059]

[Outside 12] Select according to the color you want to adjust, and increase or decrease the data of the selected color with the ← and → keys. Cursor display after setting

[0060]

[Outside 13] Set to “End” and press the OK key to exit the adjustment screen.

As described above, the original copy data is set in the minimum interrupt cycle unit of the CPU that controls the drive of the optical system motor, and the memory print data is set as the horizontal synchronizing signal H.
It is set with the cycle of SYNC as a unit. For example, in FIG.
Respectively, from the original tip L _M as in (A), L _C,
If the output (B) of a four-color copy of the same size as the original with straight lines of M, C, Y, and Bk at the distances of L _Y and L _K is given, the data of the first color

[0062]

[Outside 14] Becomes Here, w is the CPU minimum interrupt period described above.

In the case of memory printing, a pattern corresponding to the original (A) is generated in the memory 113 described above, and memory printing can be performed in the same manner. I.e.

[0064]

[Outside 15] Becomes Here, h is the cycle of the horizontal synchronizing signal HSYNC described above. And so on

[0065]

[Outside 16] (I = 2, 3, 4) and _{(L C -L C '),} (L Y -
L _Y ′), (L _K −L _K ′).

In order to improve the accuracy, for example, L _M ′ = (L _M1 ′) based on the output results of a plurality of (j) sheets.
+ ... + L _Mj ) / j can be obtained.

In the case of four-color copy or four-color print, the data obtained as described above is used in the developing order (i = 1,
2, 3, 4) are used in this order, but (i = 1, 2, 3) is used in the three-color mode, and (i = 1, 2) is used in the two-color mode.

As described above, the time data corresponding to the rotation unevenness of the transfer drum corresponding to the developing order is stored in correspondence with each of the original copy and the memory print, and based on the data, the color shift at the time of the original copy is stored. Controls the drive timing of the scanning optical system relative to the rotation of the transfer drum for each color, and the color misregistration at the time of memory printing is the output timing of the image data from the memory for each rotation of the transfer drum By performing relative control, it is possible to obtain a print output with no color misregistration during copying, memory printing, or composite printing.

(Second Embodiment) In the first embodiment, attention is paid only to the developing order. However, as described with reference to FIG. 8, in the configuration of the present embodiment, the color shift amount for the first color is one sheet. It is expected that it will be different from the second and subsequent sheets. Therefore, the accuracy can be further improved by considering the printing order. That is, as shown in FIG. 11, in the adjustment screen, “M1” for the first sheet is set as the adjustment parameter for the first color,
Two types of "M2" for the second and subsequent sheets are prepared, and in order to obtain adjustment data, a plurality of copies or prints are output, and data corresponding to "M1" is copied or It is obtained only from the first sheet of each portion of the print, and "M2" is obtained only from the second and subsequent sheets of each portion of the copy or print.

New data corresponding to "M1"

[0071]

[Outside 17] (For original copy),

[0072]

[Outside 18] (Memory print)

[0073]

[Outside 19] (For original copy),

[0074]

[Outside 20] If (for memory printing) is data corresponding to "M2", the same as in the first embodiment.

[0075]

[Outside 21] It can be defined as (i = 0, ... 4).

FIG. 12 shows the control flow of the second embodiment.

Since it is basically the same as the control flow of FIG. 7,
Only different points will be described. In step 1204, T ₁₀ and T ₂₀ for the first sheet and T ₁₁ and T ₂₁ for the second and subsequent sheets are distinguished and prepared as magenta color misregistration adjustment amounts. Then 1
"0" is set in the area i on the RAM as a color counter for the first magenta (1205). As a result, T ₁₀ and T ₂₀ are applied to the first sheet of magenta. After that, the process from paper feeding (1206) to START signal output (1218) is the same as in FIG. 7. When the color counter i reaches "4", that is, black image formation, the color counter i is set to "1" for the second magenta.
As a result, for the second and subsequent magentas, T ₁₁ and T ₂₁
Is applied.

As described above, by setting a specific condition such as a print page or setting an adjustment parameter for printing, a higher quality original copy or memory print can be output.

(Third Embodiment) In the first embodiment, adjustment parameters are provided for all developing color orders, and adjustment parameters are provided for original copy and memory print. Third
In this embodiment, the purpose is to improve the serviceability by reducing the adjustment items.

That is, as described with reference to FIG. 8 of the first embodiment, the state of suction and separation of the paper in the image forming sequence is the first.
When the color and the second and subsequent colors are different, the adjustment parameter can also be expressed by the relative relationship between the first and second colors. The adjustment screen at this time may have two types of "copy" and "print" as shown in FIG. Parameters shown in the first embodiment

[0081]

[Outside 22] Parameter corresponding to "copy" using

[0082]

[Outside 23] The parameters corresponding to "Print"

[0083]

[Outside 24] Can be defined as

The present invention is not limited to the color image forming apparatus of the type shown in FIG. 2, but a color image forming apparatus provided with a rotary developing device, other transfer type color image forming apparatus, and other type of color image forming apparatus. Is applicable to.

[0085]

As described above, in the case of forming images of a plurality of colors sequentially for each color, by providing means for setting the color misregistration adjustment parameter for each copy of the original and memory printing, It is possible to provide a color image processing apparatus capable of outputting an image without color misregistration in an apparatus capable of performing copy printing and memory printing, or a composite printing of these two types of images.

[Brief description of drawings]

FIG. 1 is a circuit configuration block diagram according to a first embodiment.

FIG. 2 is a sectional view of a color copying apparatus to which the present invention can be applied.

FIG. 3 is an explanatory diagram of color unevenness.

FIG. 4 is a structural diagram of a photosensitive drum and a transfer drum.

FIG. 5 is an explanatory diagram of a document reading unit.

FIG. 6 is an explanatory diagram of the first embodiment.

FIG. 7 is a control flow chart of the first embodiment.

FIG. 8 is an explanatory diagram of a paper transport sequence.

FIG. 9 is an explanatory diagram of an operation display according to the first embodiment.

FIG. 10 is an explanatory diagram of the first embodiment.

FIG. 11 is an explanatory diagram of an operation display according to the second embodiment.

FIG. 12 is a control flow chart of the second embodiment.

FIG. 13 is an explanatory diagram of an operation display according to the third embodiment.

[Explanation of symbols]

101 CPU 102 ROM 103 RAM 104 timer 105 timer 109 CCD 110 Image processing unit 111 selector 113 memory

Claims (2)

[Claims] 1. A color original reading unit, a color image storage unit, a color image forming unit for sequentially forming a plurality of colors on the basis of any one of image data from the reading unit and image data from the storage unit. A color image forming apparatus having image recording means includes setting means for setting color misregistration correction data and correction means for correcting color misregistration of a recorded image based on the correction data. A color image forming apparatus, wherein first correction data for recording image data from the reading unit and second correction data for recording image data from the storage unit can be set independently. . 2. The color image forming apparatus according to claim 1, wherein the image data from the reading device and the image data from the storage unit can be combined and recorded.