JPH04344666A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To provide a multicolor image forming device in which there is no possibility that the stain which is caused at the part of a control mark on a recording paper is erroneously detected as the control mark even when the stain is caused and color slurring caused by the erroneous detection is surely prevented from occurring. CONSTITUTION:A control mark TM written in the image non-formed area of a recording paper 3 is read by a read means and the dimension thereof is measured by a dimension measuring means. A command (d) for starting image recording is given by a recording start command means only when the measured dimension is a value within a specified range. Even when the stain exists ahead of the control mark TM, the command (d) is not given unless the stain is approximate to the control mark TM, so that image recording by the erroneous detection of the stain is not performed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming apparatus for forming images of different colors on the same surface of recording paper by repeatedly superimposing them for each color. The present invention relates to a multicolor image forming apparatus that records an image while preventing color misregistration by providing control marks arrayed along the feeding direction of recording paper, etc., and controlling the image recording position by reading the control marks.

0002

[Prior Art] For example, K (black) is printed on the same surface of recording paper.
, C (cyan), M (magenta), Y (yellow), etc., and a method and apparatus for repeatedly overlapping and forming images of different colors for each color are disclosed in Japanese Patent Laid-Open No. 50-80713, Publication No. 57-114158, JP-A-59-10
It is publicly known as described in Japanese Patent No. 5600 and the like. Devices of this type are widely put into practical use as thermal transfer printers, electrostatic color plotters, printing devices, and the like.

[0003] In these devices, when performing multicolor recording, if the positions of images to be superimposed do not precisely match each other, color misregistration will occur, and the quality of the formed image will deteriorate significantly. The above color shift occurs when the paper feed roller does not accurately match the movement of the recording paper when moving the recording paper back and forth, or when the recording paper itself expands and contracts due to the effects of tension, temperature, humidity, etc. on the recording paper. This occurs in cases like this. The influence of such color shift becomes particularly noticeable when forming a large-screen image, and cannot be ignored.

[0004] As solutions to such problems, for example, Japanese Patent Laid-Open Nos. 57-122455 and 1987-1
Publication No. 24753, USP No. 4401024 specification, U
As disclosed in SP4485982, etc., control marks are placed along the side edges of the recording paper, and by reading these control marks, changes in the dimensions of the recording paper, etc. can be detected, and changes in each line can be detected. There are methods and devices that adjust a recording timing signal to form recording dots at predetermined intervals that follow the expansion and contraction of recording paper. Although this type of method and device can prevent color shift in multicolor images to a certain extent, various problems remain. In view of these circumstances, various improvement proposals have been made to reduce as much as possible deviations in color overlapping due to expansion and contraction of recording paper.

For example, Japanese Patent Laid-Open No. 63-53071 discloses that for recording dots corresponding to control mark positions, the recording dot formation position is determined by a signal read from the control mark, and for other recording dots, the recording dot formation position is determined by the signal read from the control mark. In this method, color misregistration is corrected by positioning the recording dots at predetermined fixed recording paper feeding distances, starting from the recording dot positions determined based on the following.

[0006]

[Problem to be Solved by the Invention] In the above-mentioned apparatus that records images based on the control marks, it is necessary to detect the first control mark among the control marks continuously recorded in the feeding direction. Image recording is starting. Therefore, the first of the continuously recorded control marks
If there is dirt or the like at a position ahead of the 1st control mark in the feed direction, this will be mistakenly detected as the 1st control mark, and image recording will start from the erroneously detected position. become. Therefore, for example, if the recording paper becomes dirty after recording an image of the first color and a control mark is erroneously detected when recording an image of the second color, the image recording of the first color and the second and subsequent colors will be different. Since a large positional shift will occur at the starting point, a large color shift will occur. In addition, irregular color shifts occur frequently between images of the second color and the third color onwards, as a result of the lack of normal control.

[0007]An object of the present invention is to prevent even if dirt occurs in the control mark portion of the recording paper, the dirt will not be mistakenly detected as a control mark, and to reliably prevent the occurrence of color shift due to the above-mentioned false detection. An object of the present invention is to provide a multicolor image forming apparatus.

[0008]

[Means for Solving the Problems] In order to solve the above problems and achieve the objects, the present invention takes the following measures. That is, there is a writing means for writing a control mark in a non-image forming area such as a side edge of a recording paper, a reading means for reading the control mark written by this writing means, and a size of the control mark read by this reading means. a recording start command means for issuing a command to start image recording when the dimension of the control mark measured by the dimension measuring means is within a specified range; and a recording start command means for issuing a command to start image recording. and an image recording means that is started by a recording start command and records an image to be recorded on the recording paper while controlling the image recording position of each color using the control mark.

[0009]

[Effects] By taking the above measures, the following effects occur. The control mark written in the non-image forming area of the recording paper is read by the reading means, and the dimension is measured by the dimension measuring means. Then, only when the measured dimension is within a specified range, the recording start command means issues a command to start image recording. Therefore, even if there is a stain similar to the control mark at a position ahead of the control mark, the recording start command will not be issued unless the stain is extremely close to the control mark. Therefore, image recording due to erroneous detection of dirt is almost never performed. In this way, even if dirt occurs in the control mark portion of the recording paper, there is no risk of the dirt being erroneously detected as a control mark, and it is possible to reliably prevent color misregistration due to the erroneous detection.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a schematic configuration of a color electrostatic plotter as a multicolor image forming apparatus according to an embodiment of the present invention. For example, image data for each color, such as vector data and image data supplied from an image data supply means 1 such as an external computer, together with various parameters necessary for image recording, are input to a control means 2 having a TM determination function, which will be described later. The image data subjected to predetermined processing by the control means 2 is recorded on recording paper 3 loaded in the color electrostatic plotter main body 10. When recording a multicolor image, this color electrostatic plotter main body 10 has control marks TM arranged along the side edge of the recording paper 3 in the recording paper feeding direction, and then uses the control marks TM as a reference. TeK (black)
, C (cyan), M (magenta), Y (yellow).
Multicolor recording is performed by repeatedly overlapping color images for each color.

As shown in the figure, the color electrostatic plotter main body 10 includes a paper feed roll 11 on which the recording paper 3 is wound, a reading sensor 12 for reading a control mark TM to be described later,
An encoder 13, an electrostatic recording head 16 and a pad roller 15 forming a latent image forming section 14, a developing section 17 consisting of a plurality of color developing heads, a waste liquid suction section 18 that sucks up developer waste, a paper feed roller 19, and an intermediate take-up. Copy 20, recording paper 3
It has an autocross cutter 21 for cutting paper into a predetermined size, a paper discharge section 22, etc., and are arranged as shown in the figure.

The developing section 17 uses K (black), for example, to form a color image by overlapping the four colors described above.
, C (cyan), M (magenta), Y (yellow) development heads 17K, 17C, 17M, 17
It has Y.

[0013] The order of recording images of the first to fourth colors is basically arbitrary. Therefore, the developing head 17K
, 17C, 17M, and 17Y are not limited to those shown in the drawings. In addition, the paper feed roller 11 and the pad roller 1
5, the paper feed roller 19, and the intermediate take-up roller 20 are driven by a drive system (not shown).

Next, the basic operation of the color electrostatic plotter constructed as described above will be explained. First, recording paper 3
is sent out from the paper feed roll 11 in the direction of the paper discharge section 22. Then, first, the data of the control mark TM created inside the plotter or the image data supplied from the image data supply means 1 consisting of an external computer etc. is adapted to the electrostatic recording head 16 inside the control means 2. It is processed and supplied to the electrostatic recording head 16 by a recording controller of the control means 2, which will be described later. Therefore, a recording voltage corresponding to each data is applied to a predetermined position on the recording paper 3, and a latent image of recording dots is formed. When the portion of the recording paper on which the latent image of recording dots has been formed comes to the position of the developing section 17, one of the developing heads of the color corresponding to the image data, for example, K (
The developing head 17K (black) rises and contacts the recording paper 3. Therefore, a developer is applied to the latent image forming area to perform development. When the portion of the recording paper on which this development has been performed comes to the position of the waste liquid absorbing section 18, this waste liquid absorbing section 18
The waste liquid remaining on the recording paper 3 is sucked out, removed, and dried. This dry recording paper 3 is wound onto an intermediate winding section 20. Afterwards, recording paper 3
The film is rewound to its original position, that is, to the position of the latent image forming section 14.

The above operation is repeated a plurality of times, that is, for the number of colors corresponding to four colors. When the last color image is developed, the recording paper 3 is conveyed toward the paper discharge section 22, and the portion of the recording paper on which the image has been formed is cut into a predetermined size by the autocross cutter 21 and then discharged. The liquid is discharged from the unit 22 to the outside of the apparatus.

By the way, in the above-mentioned image recording operation, the control mark TM is placed on the recording paper 3 in advance by the action of the control means 2.
This control mark TM is read by the reading sensor 12, and in synchronization with this, that is, color images of each color are recorded in an overlapping manner at accurate timing.

FIG. 2 is a block diagram showing a detailed configuration of the control means 2 having a control mark determination function. First, terminal 2
3 to the CPU 30, when data from an external computer or the like, that is, length data in the recording paper feeding direction of the image data to be recorded from now on, is input to the CPU 30.
The CPU 30 sets length information a of the control mark TM necessary for this length data in the TM pattern generator 31. Next, the recording paper 3 is sent out, and the CPU 30 sends T
The M pattern generator 31 is instructed to start recording the control mark TM, and the selection circuit 32 is given a switching command b. Therefore, the selection circuit 32 is switched to the TM side. Then, the TM pattern generator 31
A pattern is generated, and image data c of this TM pattern is sent to the recording controller 33 via the selection circuit 32. For this reason, a recording signal corresponding to the image data c of the TM pattern is given to the electrostatic recording head 16 from the recording controller 33 and recorded on the recording paper 3.

The recording controller 33 includes the selection circuit 32
It controls a series of operations until the image data c of the TM pattern obtained through the TM pattern is actually recorded on the recording paper 3, and is controlled by the CPU 30. Further, this recording controller 33 receives a pulse signal e from the encoder 13.
Line correction, which will be described later, is performed based on the pulse signal f from the reading sensor 12.

FIG. 3 is a diagram showing control marks TM recorded based on the image data c of the TM pattern. As shown in FIG. 3, the control mark TM is, for example, a periodic repetition of black and white parts. In this embodiment, the width V of the black portion and the width W of the white portion are both set to 2 mm.

Returning to FIG. 2, the explanation will be returned to FIG. The reading sensor 12 detects the black part of the image data c of the TM pattern and sends the pulse signal f to the CPU 30 and the recording controller 3.
Send to 3. After the control mark TM of the required length is recorded on the recording paper 3 as described above, the recording paper 3 is rewound to its original position. Then, it waits until a predetermined amount of image data arriving at the terminal 24 from the image data supply section 1 is accumulated in the data buffer 34. Thereafter, the recording paper 3 is fed out, and the selection circuit 32 is switched to the image data side ID in response to a switching command b from the CPU 30. CPU
When a recording start command d is sent from 30 to the recording controller 33, the recording controller 33 supplies the image data sent through the selection circuit 32 to the electrostatic recording head 16 and records it. The image data sent via the selection circuit 32 is one line data extracted from the image data stored in the data buffer 34 according to the read signal of the control mark TM recorded before being detected by the read sensor 12. This is image data extracted line by line by the circuit 35.

The recording start command d from the CPU 30 to the recording controller 33 can be issued at any time. Therefore, if a recording start command d is given from the CPU 30 to the recording controller 33 before the position of the first recording point P of the control mark TM shown in FIG. , recording of image data is started based on the read data of the control mark 41 located at the top position.

[0022] The time when the position of the first recording point P of the control mark TM reaches the reading sensor 12 is longer than the expected position of the first recording point P reaching the reading sensor 12, since there are variations among individual devices. The recording start point must be moved somewhat forward. However, if there is dirt in the area in the leading direction of the recording paper from the leading recording point P, there is a fear that the reading sensor 12 will detect the dirt as a control mark, and that normal printing will not be performed.

However, in this embodiment, the reading sensor 1
After the CPU 30 confirms that the detection signal from 2 is indeed a regular control mark, a recording start command d is sent to the recording controller 33. That is, as described above, after the control mark TM is recorded on the recording paper 3, the recording paper 3 is once rewound to its original position. Then, it waits until a predetermined amount of image data sent from the image data supply means 1 is accumulated in the data buffer 34. Thereafter, the recording paper 3 is fed out until the reading signal f from the reading sensor 12 is sent to the CPU 30. The read signal f from the read sensor 12 is sent to the CPU 3.
0, the CPU 30 including the dimension measuring means,
The pulse signal e from the encoder 13 measures the dimension until the signal of the black part of the control mark TM changes to the signal of the white part. Then, it is determined whether this value is appropriate as a control mark, that is, whether it is a false detection due to dirt, etc.
The determination is made by the CPU 30. In this embodiment, the range of this criterion is 2 mm±0.2 mm. This value is determined as an appropriate value based on experimental results, and is stored in the ROM 36 that can be read by the CPU 30, and can be easily changed.

The CPU 30, which includes a recording start command means, issues a recording start command d to the recording controller 33 only when the detected value is determined to be appropriate as a result of the above determination. As a result, the recording controller 33 starts recording image data in response to the detection signal f of the second control mark 42 from the reading sensor 12.

In this embodiment, the CPU 30 measures the dimension until the signal for the black portion of the control mark TM changes to the signal for the white portion using the pulse signal e from the encoder 53, and determines whether this value is appropriate for the control mark TM. However, at this time, the above-mentioned measurement is performed only once to determine whether the control mark TM is suitable or not. However, in order to reduce the probability of false detection due to a measurement error of the control mark TM, after repeating the above measurement several times, the control mark TM
It is also possible to judge whether or not it is appropriate. This measurement count is stored in the ROM 36 and can be easily changed.

[0026] Through the above procedure, the CPU 30 controls the recording controller 33.
When the recording start command d is given to the recording controller 33, the recording controller 33 processes the image data sent via the data buffer 34, one-line data extraction circuit 34, and selection circuit 32 according to the signal from the reading sensor 12. Record.

The recording controller 33 receives signals from the encoder 13 in order to control the recording density so that a data string of 64 lines exists in the total width of the black part and white part of the control mark TM, that is, during one period T. Recording is performed line by line using the pulse signal e.

As shown in FIG. 4(a), the "
Due to causes such as "shrinkage," the line data may be subject to control marks TM.
If a positional shift occurs due to two or more lines in excess, the excess condition is corrected by deleting predetermined line data (64th line).

Furthermore, as shown in FIG. 4(b), the recording paper 3
If the line data is misaligned with the control mark TM by two or more lines due to "elongation" or other causes, the problem can be corrected by copying and recording the predetermined line data (64th line). Correct the deficiency condition.

The above-mentioned value of ``2 lines or more'' is a value determined based on experimental results, recognizing that 2 lines is an acceptable amount in terms of image quality. The correction may be made by setting a large value or a small value. This line change is also easy. Note that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0031]

According to the present invention, the control mark written in the non-image forming area of the recording paper is read by the reading means, and its dimension is measured by the dimension measuring means. Then, only when the measured dimension is within a specified range, the recording start command means issues a command to start image recording. Therefore, even if there is a stain similar to the control mark at a position ahead of the control mark, the recording start command will not be issued unless the stain is extremely close to the control mark. Therefore, image recording due to erroneous detection of dirt is almost never performed. In this way, even if dirt occurs in the control mark portion of the recording paper, there is no risk of misdetecting the dirt as a control mark, and a multicolor image forming apparatus is provided that can reliably prevent color shift caused by such misdetection. can.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a color electrostatic plotter as a multicolor image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of a control means having a control mark determination function according to the same embodiment.

FIG. 3 is a diagram showing control marks TM recorded based on image data of a TM pattern according to the same embodiment.

FIG. 4 is an explanatory diagram of line correction for line data according to the same embodiment.

[Explanation of symbols]

1... Image data supply means, 2... Control means, 3... Recording paper,
10... Color electrostatic plotter, 11... Paper feed roll, 12...
Reading sensors 12, 13...encoder, 14...latent image forming section, 16...electrostatic recording head, 15...pad roller, 1
7... Developing section consisting of multiple color developing heads, 18... Waste liquid absorbing section, 19... Paper feeding roller, 20... Intermediate winding section,
21...Auto cross cutter, 22... Paper discharge section.

Claims (1)

[Claims] 1. A multicolor image forming apparatus that records control marks on recording paper and controls the image recording position of each color of an image supplied based on image data of a plurality of colors to be recorded according to the control marks. A writing means for writing the control mark in a non-image forming area of the recording paper, a reading means for reading the control mark written by the writing means, and a dimension measurement for measuring the size of the control mark read by the reading means. means and
a recording start command means for issuing a command to start image recording when the dimension of the control mark measured by the dimension measuring means is within a specified range; A multicolor image forming apparatus comprising: an image recording means for recording an image to be recorded on the recording paper while controlling the image recording position of each color using control marks.