JP4456850B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image by ejecting ink while scanning an inkjet recording head.

As image processing devices (image forming devices) such as printers and copiers have improved in image quality and color, there is a social problem that specific manuscripts that should not be originally copied, such as banknotes and securities, are copied and used. May occur. In order to prevent the occurrence of this problem, there is a technique for specifying an output image processing apparatus by adding a specific pattern such as a device number (hereinafter referred to as a tracking pattern) to an output image of the image processing apparatus. It was known.
However, the above technology has been used in high-quality laser-type page printers, but the image quality of low-cost inkjet printers for individual users has rapidly improved. It is no longer inferior.
In the ink jet method, when a carriage is moved and ink is ejected from nozzles provided on a head in the carriage, and an image is formed on a recording medium, the current nozzle position in the main scanning direction (carriage moving direction) is linearly changed. In general, control is performed by counting the pulses obtained from the encoder, and generating ink injection timing based on the pulses.
That is, since image formation is performed in units of carriage scans, the printing speed is a disadvantageous principle compared to page printers. Therefore, in general, an inkjet printer detects a portion without white image data (white portion) and controls to move the paper so that the portion is not scanned, thereby increasing the printing speed with the minimum number of carriage scans. .
As a related technique, for example, Patent Document 1 proposes generation of a trace pattern by a printer driver on the host side. Patent Documents 2 to 5 propose techniques for adding a digital watermark for preventing forgery and a tracking pattern to a printed image with less influence on image quality.
Patent Document 6 proposes a technique for preventing the tracking pattern itself from being counterfeited and adding the tracking pattern with certainty. Patent Document 7 proposes a technique that enables forgery prevention and tracking by identifying a specific image and controlling whether or not a tracking pattern is added. Patent Document 8 proposes a technique for making a tracking pattern stand out in order to prevent the tracking pattern from being misused because it is difficult to visually determine it.
JP 2000-313156 A JP 2002-010057 A JP 2002-076604 A Japanese Patent Application Laid-Open No. 07-107279 Japanese Patent Laid-Open No. 07-123229 JP 2002-300366 A Japanese Patent Laid-Open No. 06-340112 JP-A-11-275354

When adding a tracking pattern for the purpose of preventing forgery as described above in an ink jet printer or copying machine, the tracking pattern is also added to a blank portion that originally has no image data, and an effective image (printing) is printed on the paper area. The smaller the number of (parts), the more the original printing is performed with a smaller number of scans, but the entire surface is scanned, and the printing speed is significantly reduced.
In the laser method, image data is handled in units of pages, so there is no particular restriction on the tracking pattern insertion. However, in the ink jet method, the effective image part (the part to be scanned) can be extracted in scan data that matches the head. However, scan data may not have continuity because processing aiming at high image quality such as interlace and multi-pass is performed depending on the print mode. In this case, if a tracking pattern is to be added, the tracking pattern must be prepared for each print mode, which complicates.
SUMMARY An advantage of some aspects of the invention is that it provides an inkjet image forming apparatus capable of adding a tracking pattern for preventing forgery without impairing printing productivity.

In order to achieve the above object, the invention described in claim 1 is an ink jet system that forms an image on a recording medium in units of scans of the carriage by moving the carriage and ejecting ink from nozzles of a head held by the carriage. The image forming apparatus includes a tracking pattern generation unit that generates a tracking pattern to be added and a tracking pattern addition unit that adds the tracking pattern to image data before the scan data generation unit of the carriage, and generates the scan data. The unit includes a tracking pattern detection unit having a line pixel counter for each color and a line pixel number calculation unit, and the tracking pattern detection unit includes the number of pixels for each line of the input image data and the number of line pixels for only the tracking pattern. And the number of pixels of the color used in the tracking pattern is the same as the number of line pixels in the tracking pattern only. If the number of pixels of other colors is not present, the line only has a tracking pattern and it is determined that there is no image data. Control is performed so as not to perform scanning .
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the tracking pattern generation unit includes a tracking pattern information holding unit that holds tracking pattern information generated by the tracking pattern generation unit, and the tracking The pattern detection unit loads the pattern information held in the tracking pattern information holding unit, and calculates the number of pixels of the line of the tracking pattern only in the line pixel number calculation unit based on the information. .
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect , the tracking pattern detection unit has a tracking pattern line counter, and the tracking pattern is repeatedly synthesized on the entire page for each block having a predetermined number of lines. If it is, it is determined whether only the tracking pattern exists for each block counted by the tracking pattern line counter .

  In the present invention, the tracking pattern generation unit that generates the tracking pattern to be added and the tracking pattern addition unit that adds the tracking pattern to the image data are provided in the preceding stage of the scan data generation unit of the carriage. Aim can be achieved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an external view of an ink jet printer. The ink jet recording head 1 has a nozzle row in the head scanning direction (hereinafter referred to as the main scanning direction), and an ink tank is integrated or separated, and in the case of being integrated, is mounted on the carriage 2 together with the recording head. The carriage 2 is reciprocated in the directions of arrows A and B along the guide rail 5 via the timing belt 4 by the moving motor 3.
On the other hand, in order to synchronize with the movement of the carriage, synchronization signal generating means is provided. Specifically, the synchronization signal generating means is a linear in which slits are drawn on a transparent film at a recording pitch density corresponding to, for example, 180 dots / inch (dpi) or 360 dpi, and slits having different widths are drawn at constant intervals. An optical encoder configured by fixing the encoder 6 to the apparatus main body and mounting a detection unit 7 made of a photo interrupter or the like on the carriage 2 in order to detect the slit of the linear encoder 6. Enables position detection. Further, a flexible printed circuit board (not shown) for extracting an output signal from the photo interrupter to the outside is connected to the main body of the detection unit 7 and is connected to a circuit unit (not shown).
The feeding roller 10 sandwiches the recording material 11 and feeds the recording material 11 in the D direction. The recording material 11 fed by the feeding roller 10 is wound around the platen roller 8 and fed in the F direction. Further, the gap between the recording material 11 wound around the recording head 1 and the platen roller 8 is constant. When the recording head 1 moves to G along the guide rail 5, the recording head 1 faces the head cleaning means 12 and is capped at the time of cleaning and storage of the ink discharge nozzles. In the recording head 1, a plurality of nozzle rows are arranged with a certain interval, and ink of each color is ejected from each nozzle to realize color printing. When moving once along the guide rail 5, the writing of the recording width d is completed.
FIG. 2 is an external view of the inkjet multifunction peripheral. A scanner unit 13 is provided in the ink jet printer, and the scanner unit 13 has a pressing plate 14 for pressing a document. The main body 15 has a function equivalent to that of an ink jet printer, but various image processing such as color conversion from RGB to YMCK and gamma correction is performed on image data of a document read by a scanner.

FIG. 3 is a control block diagram of the image forming apparatus of the present invention. This example is an inkjet-type multifunction peripheral, and includes a scanner 20 (scanner unit 13 in FIG. 2), a printer controller 21, an image processing unit 22, a device information storage unit 23, a tracking pattern generation unit 24, and a tracking pattern generation unit 24. Tracking pattern information holding unit 25, tracking pattern adding unit 26, scan data generating unit 27, memory 33, motor control unit 34, and inkjet engine 35. The scan data generation unit 27 includes a tracking pattern detection unit 28 including a tracking pattern information load unit 29, a line pixel number calculation unit 30, a line pixel counter 31, and a tracking pattern line counter 32.
Conventionally, in laser printers and multifunction machines, the tracking pattern is generally synthesized at the final stage of transferring data to the laser engine. In the ink jet system, the final data to be transferred to the engine is scan data to be sent to the carriage head, and in the case of the ink jet system, it generally has a plurality of print modes (carriage scan methods).
This is a characteristic of the ink jet system. When priority is given to the printing speed, the width of the nozzle row of the head is scanned once to form an image corresponding to the head width. In the case of image quality priority, after scanning once, the paper moves in the sub-scanning direction at a distance of half the nozzle pitch, and the scanning is performed again to double the resolution of the nozzle pitch (interlace processing). Various scans such as thinning out pixels in the main scanning direction, scanning once, and filling in the dots that were thinned out in the next scan to prevent interference between adjacent dots (multipass) Has a print mode.
4 (1) to 4 (2) and FIG. 5 are explanatory diagrams of the print mode when image quality is prioritized. (1) is the original page image. When the interlace processing is performed, the scan data is divided in the sub-scanning direction as shown in (2). Further, FIG. 5 shows a case where multipath processing is performed in addition to interlace. Since it is divided in the main scanning direction, the original shape no longer remains as shown in the figure. Actually, this interlace and multipath become more complicated as the image quality increases.
After the scan data is generated in this way, the image data has lost its continuity, so when trying to add a tracking pattern, each scan data is also divided in the same manner as the image data. Therefore, tracking pattern generation requires a different process for each print mode, and is complicated.

6 is an image data flow diagram (see S1 to S8), and FIG. 7 is a tracking pattern generation flowchart (see S11 to S14). Embodiment 1 will be described with reference to FIGS. 3, 6, and 7. The image data to be printed is a copy original image input from the scanner 20 and electronic data (printer language or compressed data) sent from the host.
In the case of a copy image, the image processing unit 22 performs various processes for printing such as YMCK color conversion and gamma correction. In the case of a printer, rendering (development from printer language to bitmap data) is performed by the printer controller 21, or bitmap compressed data rendered on the host base is decompressed.
At this stage, the tracking pattern adding unit 26 synthesizes the tracking pattern with the image data from the copy and printer. The tracking pattern to be synthesized is read and generated by the tracking pattern generation unit 24 from the device information storage unit 23 that stores device-specific information (such as a manufacturing number).

FIG. 8 is a tracking pattern detection flowchart (see S21 to S25). A second embodiment will be described with reference to FIGS. 3, 6, and 8. The scan data generation unit 27 converts the image data combined with the tracking pattern into a format that matches the nozzle array (head) that ejects ink mounted on the carriage.
At this time, the presence / absence of print data is detected in units of lines or in units of blocks, and when there is a certain number of lines (the minimum amount of paper transportable movement) without image data, the part is notified to the motor control unit 34. Then, control is performed so that the carriage is not scanned.
By this control, printing can be performed by skipping blank portions without image data, so that the printing speed can be increased. The tracking pattern detection unit 28 corresponds to the conventional part for detecting the presence or absence of print data. Here, the tracking pattern information loading unit 29 loads the pattern information held in the tracking pattern information holding unit 25 in the tracking pattern generation unit 24 described above, and the line pixel number calculation unit 30 based on the information loads the pattern information. Calculate the number of pixels in the line of the tracking pattern only.
The number of pixels (for each color) of the input image data for each line is counted by the line pixel counter 31 and compared with the number of line pixels of the tracking pattern only, and the number of pixels of the color used in the tracking pattern. Coincides with the number of line pixels of the tracking pattern only, and when the number of pixels of other colors is 0, it is determined that this line exists only in the tracking pattern and there is no image data.
When a line having no image data continues for a certain number of lines, the motor control unit 34 is notified to transport (skip) the paper in the sub-scanning direction for the blank portion (only the trace pattern). Thereafter, the printing operation is performed by generating scan data and transferring the generated scan data to the inkjet engine 35 under the same control as conventionally detecting a blank line, and performing carriage movement and paper conveyance by motor control. In addition, a tracking pattern is generated in the first embodiment, and information on the generated tracking pattern is held in the tracking pattern information holding unit 25.

FIGS. 9A to 9C are diagrams showing examples of tracking patterns. (1) shows the configuration of the tracking pattern. In this example, the pattern is expressed by a matrix of 8 × 8 dots, and the color to be used is one yellow color. In addition, if the 1-pixel multi-bit configuration is used, more information can be expressed. In this example, unique information of the device is assigned to the total 64 bits by the tracking pattern generation unit 24.
(2) shows the actual pattern. The dot in the frame indicates “1”, and this is the portion where the actual dot is hit. (3) shows information held in the tracking pattern information holding unit 25, which has the number of “1” existing in each line (8 lines in this example). Next, the tracking pattern information held by the tracking pattern information loading unit 29 is loaded into the line pixel number calculation unit 30. The line pixel number calculation unit 30 calculates the number of pixels of the tracking pattern in one line.
FIG. 10 is a diagram illustrating an example of calculating the number of line pixels. The main scanning effective pixel number is a value that varies depending on the paper size and margin width, and the tracking pattern pixel number is the loaded tracking pattern information. Based on the result calculated here, by comparing with the number of pixels for each line and color of actually input image data, it is a line of only a tracking pattern or a line containing image data. Is determined.

In the second embodiment, it is assumed that the number of pixels of only the tracking pattern to be compared with the number of pixels of each line of the input image data is that the tracking pattern is repeatedly synthesized on the entire page for each block (for the synthesis method) In this example, it is repeated every 8 lines.
Therefore, if the tracking pattern starts on the basis of the page head line, a counter for every 8 lines (in this example, a 3-bit DOWN counter) is prepared, and data associated with the counter value, that is, tracking pattern information is referred to and compared. Thus, line pixel information having a correct tracking pattern can always be used as a comparison reference within a page.
FIG. 11 is a diagram illustrating an example of a tracking pattern line counter. In the figure, the count value of the tracking pattern line counter 32 is loaded with the vertical value of the tracking pattern (in this case, a value of -1) in the hatched portion, and is down-counted by the line synchronization signal. In each line, the number of line pixels of the tracking pattern to be referred to is shown at the bottom.
With the configuration and control described above, it is possible to perform motor control in which a blank portion is detected from image data with a tracking pattern added to the entire page, and the carriage is not scanned as a blank portion. FIGS. 12 (1) and 12 (2) show a print image in which a portion without an image (text or picture) is not scanned.
The present invention is configured and operated as described above, and has the effect of being able to respond to each printing mode with a single control and add a tracking pattern without impairing the printing productivity by carriage scan control peculiar to the ink jet method. can get. Since the tracking pattern can be added before the scan data is generated, it is not necessary to be aware of the print mode, and the control can be simplified simply by adding the same pattern.
In addition, since the information of the added tracking pattern can be known at the time of pattern detection, it is possible to detect a line of only the tracking pattern and determine a blank portion regardless of what pattern is added. In addition, even in the middle of the page, the tracking pattern can be detected correctly because the number of lines of the added tracking pattern is always known.

1 is an external view of an ink jet printer. 1 is an external view of an inkjet multifunction device. FIG. 3 is a control block diagram of the image forming apparatus of the present invention. Explanatory drawing of the printing mode at the time of image quality priority. Explanatory drawing of the printing mode at the time of image quality priority. Image data flow diagram. Tracking pattern generation flow diagram. Tracking pattern detection flowchart. The figure which shows the example of a tracking pattern. The figure which shows the line pixel number calculation example. The figure which shows the example of a tracking pattern line counter. The figure which shows the example of a line skip.

Explanation of symbols

24 tracking pattern generation unit, 25 tracking pattern information holding unit, 26 tracking pattern addition unit, 27 scan data generation unit

Claims (3)

In an inkjet image forming apparatus that moves a carriage and ejects ink from nozzles of a head held by the carriage to form an image on a recording medium in units of scanning of the carriage.
A tracking pattern generation unit that generates a tracking pattern to be added, and a tracking pattern addition unit that adds the tracking pattern to image data, in a stage preceding the scan data generation unit of the carriage ,
The scan data generation unit includes a tracking pattern detection unit having a line pixel counter and a line pixel number calculation unit for each color,
The tracking pattern detection unit compares the number of pixels per line of the input image data with the number of line pixels of the tracking pattern only, and the number of pixels of the color used in the tracking pattern is a line pixel of the tracking pattern only If the number matches the number and there is no number of pixels of other colors, it is determined that the line has only a tracking pattern and there is no image data.
An image forming apparatus that performs control so that a carriage is not scanned in a blank portion when lines having no image data continue for a certain number of lines . The image forming apparatus according to claim 1.
The tracking pattern generation unit has a tracking pattern information holding unit for holding tracking pattern information generated by the tracking pattern generation unit;
The tracking pattern detection unit loads the pattern information held in the tracking pattern information holding unit, and calculates the number of pixels of the line of the tracking pattern only in the line pixel number calculation unit based on the information. An image forming apparatus. The image forming apparatus according to claim 1 or 2 ,
When the tracking pattern detection unit has a tracking pattern line counter, and the tracking pattern is repeatedly synthesized on the entire page for each block of a predetermined number of lines, the tracking pattern for each block counted by the tracking pattern line counter An image forming apparatus that determines whether or not only the image forming apparatus exists .

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