JP4458038B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

Conventionally, in order to suppress counterfeiting of securities such as banknotes, an additional pattern (specific pattern) made up of a plurality of dots has been embedded as tracking information in an image. Such an additional pattern is read by a dedicated reading device after printing, but is read if the additional pattern overlaps the input image (dots constituting the tracking information overlap dots constituting the image). I can't. Therefore, the additional pattern is periodically and repeatedly applied to the entire surface of the recording medium. With such a configuration, it is possible to attempt to read the additional pattern at a plurality of locations, and therefore it is expected that the additional pattern can be read without any trouble by the reader after printing (Patent Document 1).
JP 11-122470 A

However, even in the above case, information about the additional pattern (grating width, arrangement cycle, etc.) is known to a third party in advance by some means, and intentionally has the same cycle as the additional pattern. If an image is embedded or if an image having the same cycle as the additional pattern exists by chance, the additional pattern cannot be read accurately after printing.
The present invention has been completed based on the above circumstances, and an object thereof is to make it possible to read a specific pattern more reliably.

  As means for achieving the above object, the invention according to claim 1 is characterized in that image formation is performed by adding a plurality of specific patterns regularly arranged with a plurality of dots based on a reference point to an image to be formed. The apparatus includes adjustment means for adjusting the distance between adjacent reference points to be irregular.

  According to a second aspect of the present invention, in the first aspect, the specific pattern has a lattice width a and a number of lattices c in the X direction, a lattice width b and a number of lattices d in the Y direction. The plurality of dots are regularly arranged on the basic lattice, and the adjusting means is within a range in which the overlap between adjacent basic lattices is less than a in the X direction and less than b in the y direction. And the adjustment is performed.

  According to a third aspect of the present invention, in the apparatus according to the second aspect, the adjusting means is configured such that when the product of a and c is ac and the product of b and d is bd, the reference points between adjacent specific patterns are The basic arrangement is that the distance in the X direction is ac and the distance in the Y direction is bd, and the adjustment is performed based on this basic arrangement.

  The invention according to claim 4 is characterized in that, in the adjustment according to claim 2 or 3, the movement direction of the reference point when making the adjustment is unified in one direction in both the X direction and the Y direction. Have

  According to a fifth aspect of the present invention, in the apparatus according to any one of the second to fourth aspects, the adjustment means adjusts the adjustment to a dod constituting one specific pattern and another adjacent to the dod. It is characterized in that the distance between the dods constituting the specific pattern is at least a distance in the X direction and b distance in the Y direction.

<Invention of Claim 1>
According to the invention of claim 1, the position of the reference point of the specific pattern is adjusted to be irregular. In this way, if the positions of the reference points of the specific pattern are irregular, it is possible to avoid the situation that any specific pattern is difficult to read due to the overlap with the image, and to improve the probability of reading the specific pattern. I can do it.

<Invention of Claim 2>
According to the invention of claim 2, the overlap between the basic lattices of adjacent specific patterns is set to be less than a in the X direction and less than b in the y direction. With such a configuration, dods constituting the patterns do not overlap between adjacent specific patterns. Therefore, it becomes easy to recognize the specific pattern after the image formation.

<Invention of Claim 3>
According to the invention of claim 3, the basic arrangement of the specific pattern is a state in which the basic grids of the adjacent specific patterns are arranged without leaving a gap. With such a configuration, more specific patterns can be added. Therefore, the probability that the specific pattern can be read after image formation is further increased.

<Invention of Claim 4>
For example, regarding the movement in the X direction, if the reference point can be moved in both the “+ X direction” and the “−X direction”, “+”, “ It is necessary to consider the two directions of “-”, which complicates the arithmetic processing. In this regard, according to the invention of claim 4, since the movement direction of the reference point is unified in one direction, the arithmetic processing can be simplified and the processing load can be reduced.

<Invention of Claim 5>
According to the invention of claim 5, the distance between the dod constituting one specific pattern and the dod constituting another specific pattern adjacent to the specific pattern is ensured to be equal to or larger than the lattice width. With such a configuration, an interval between dots is kept in an optimum state between adjacent specific patterns. Therefore, it becomes easier to recognize the specific pattern after image formation.

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS.
1. Overall Configuration FIG. 1 is a side sectional view of a main part of a laser printer. In the following description, for the front and rear directions, the front direction of the apparatus will be described as the front side (the right side in FIG. 1).
A laser printer (corresponding to an example of an image forming apparatus of the present invention) 1 is configured as a four-cycle color laser printer, and has a sheet feeding unit 7 that accommodates sheets 5 as recording media in a stacked manner on the bottom side of a main casing 3. A paper transport path Y is formed above the paper transport path Y.

  The sheet conveyance path Y is as shown by a solid line in FIG. 1, and is reversed at about 180 degrees to the rear of the laser printer 1 at the upper front portion of the paper feeding unit 7 and then toward the rear portion of the laser printer 1. Then, when reaching the rear end side, this time, it is reversed forward by about 180 degrees to take a path to the paper discharge tray 69 provided on the upper surface wall of the main casing 3. As will be described in detail below, a toner image in the process of being conveyed through the sheet conveyance path Y is formed on the sheet fed from the sheet feeding unit 7, and this is thermally fixed by the fixing unit 29 so as to be desired. Images are formed.

2. Configuration of Each Unit The sheet feeding unit 7 includes a sheet feeding tray 11, a sheet feeding roller 13, a conveying roller 15, and a registration roller 17. The paper feed roller 13 takes out the paper 5 one by one, and the transport roller 15 transports the fed paper 5 to an image forming position (a contact position with a transfer roller 27 described later).

  The image forming unit 9 includes a scanner unit 21, a process unit 23, and an intermediate transfer belt mechanism unit 25. The scanner unit 21 includes a laser light emitting unit (not shown), a polygon mirror, a plurality of lenses, and a reflecting mirror. In the scanner unit 21, a belt photoconductor (OPC: Organic Photo Conductor) that moves along the sub-scanning direction by passing or reflecting the laser light emitted from the laser light emitting section through a polygon mirror, a reflecting mirror, and a lens. ) Irradiate the surface of 33 by high-speed scanning along the main scanning direction.

  The process unit 23 includes a belt photoreceptor mechanism unit 31 and a developing cartridge 35. The belt photoreceptor mechanism 31 includes a first belt photoreceptor roller 39, a second belt photoreceptor roller 41, a third belt photoreceptor roller 43, and a belt wound around these three photoreceptor rollers 39, 41, 43. The photoconductor 33 is a main component, and a belt photoconductor charger 45, a potential adder 47, and a potential gradient controller 49 are additionally provided.

  The surface of the belt photoconductor 33 is uniformly positively charged by the belt photoconductor charger 45 and then exposed by high-speed scanning of laser light from the scanner unit 21. Since the charged portion is eliminated in the exposed portion, an electrostatic latent image is formed on the surface of the belt photosensitive member 33 in which a positively charged portion and an uncharged portion are arranged.

  The developing cartridge 35 includes a developing roller 37, a separation solenoid 38, a supply roller (not shown), a toner storage unit, and the like, and is dedicated to each color, that is, a yellow developing cartridge 35Y that stores yellow toner, and cyan toner. Are provided, a cyan developing cartridge 35C containing magenta toner, a magenta developing cartridge 35M containing magenta toner, and a black developing cartridge 35K containing black toner.

  These developing cartridges 35K, 35C, 35M, and 35Y are arranged in the vertical direction with the developing roller 37 facing the belt photosensitive member 33, and drive the separation solenoids 38K, 38C, 38M, and 38Y. As a result, the developing rollers 37K, 37C, 35M, and 35Y can be brought into contact with the surface of the belt photosensitive member 33 individually.

  Then, for example, when the developing roller 37Y of the yellow developing cartridge 35Y is brought into contact with the belt photoreceptor 33 on which the electrostatic latent image is formed (the other developing rollers are separated), the positively charged yellow toner Adheres only to the uncharged portion of the belt photoreceptor 33. As a result, a yellow visible image is formed on the belt photoreceptor 33.

  The intermediate transfer belt 51 constituting the intermediate transfer belt mechanism unit 25 is for sequentially transferring visible images of respective colors formed on the belt photoreceptor 33 to form a color image (toner image). The first intermediate transfer belt roller 53, the second intermediate transfer belt roller 55, and the third intermediate transfer belt roller 57 are supported by three rollers. An intermediate transfer belt roller 53 is disposed opposite to the intermediate transfer belt roller 53. Therefore, in the previous example, when the belt photoconductor 33 moves, the yellow visible image is transferred to the surface of the intermediate transfer belt 51 when facing the intermediate transfer belt 51.

  In order to form a color image on the intermediate transfer belt 51, it is necessary to transfer other colors other than yellow. For this purpose, the same transfer procedure as that for yellow may be repeated. That is, if the image is a magenta visible image, the magenta separation solenoid 38M is driven to contact only the developing roller 37M of the magenta developing cartridge 35M with the belt photosensitive member 33.

  As a result, a magenta visible image is formed on the belt photoreceptor 33. The magenta visible image has already been transferred to the yellow visible image when the belt photosensitive member 33 moves and the magenta visible image faces the intermediate transfer belt 51 in the same manner as described above. Then, the image is transferred onto the intermediate transfer belt 51 in an overlapping manner. Such a similar operation is repeated with cyan toner accommodated in the cyan developing cartridge 35C and black toner accommodated in the black developing cartridge 35K, whereby a color image is formed on the intermediate transfer belt 51. .

  The transfer roller 27 is for collectively transferring the color image formed on the intermediate transfer belt 51 onto the paper 5, and is formed by coating a roller made of a conductive rubber material on a metal roller shaft. . The transfer roller 27 is disposed opposite to the third intermediate transfer belt roller 57 with the intermediate transfer belt 51 interposed therebetween. Therefore, the color image formed on the intermediate transfer belt 51 is transferred onto the paper 5 by the transfer roller 27 while the paper 5 passes between the intermediate transfer belt 51 and the transfer roller 27.

  The fixing unit 29 is disposed behind the intermediate transfer belt mechanism unit 25, and includes a heating roller 61, a pressing roller 63 that presses the heating roller 61, and a pair of downstream rollers of the heating roller 61 and the pressing roller 63. A conveyance roller 65. The heating roller 61 includes a halogen lamp for heating, with an outer layer made of silicon rubber and an inner layer made of metal. The heating roller 61 heat-fixes the color images collectively transferred onto the paper 5 by the transfer roller 27 while the paper 5 passes between the heating roller 61 and the pressing roller 63.

3. Electrical Configuration Next, the electrical configuration of the laser printer 1 will be described. FIG. 2 is a block diagram conceptually showing the electrical configuration of the laser printer 1. The control device 90 includes a CPU 91, a ROM 92, a RAM 93, an image memory 94, a control unit 97, an additional information memory 110, and an additional pattern generation unit 100 as shown in FIG. Reference numeral 95 denotes an interface (IF) for connecting to an external device such as a personal computer (PC) 150.

  The ROM 92 stores various control programs for controlling the printer 1, and the RAM 93 is used as a work area from which various control programs are read. The image memory 94 temporarily stores image data obtained by developing a print job received through the interface 95.

  The additional information memory 110 stores additional information such as the manufacturer name of the laser printer 1, the printer model name, the transmission date and time of the print job sent along with the print job, and the user name. The additional pattern generation unit 100 generates an additional pattern B (corresponding to an example of the specific pattern of the present invention) B as tracking information based on the additional information stored in the additional information memory 110.

  The control unit 97 is composed of an ASIC (Application Specific Integrated Circuit), and is electrically connected to the image forming unit 9 described above, the operation unit 98 including an input panel, and the display unit 99 including various lamps. The CPU 91 controls each of these units, that is, the control unit 97, the image memory 94, the additional information memory 110, and the additional pattern generation unit 100 according to a flowchart described below to form a color image on the paper 5. is there.

FIG. 3 is a flowchart showing the flow of print processing executed by the CPU 91.
When the power of the laser printer 1 is turned on by the operator, first, initialization processing (for example, processing for initializing the RAM 93, the image memory 94, and the additional information memory 110) is performed by the CPU 91, and then from the host device. The process waits for a print job to be transmitted (step 10). Then, when a print job is transmitted from the personal computer 150 as the host device, this is received by the control device 90 through the interface 95 (step 20).

Then, the process proceeds to step 30 following the reception of the print job. In step 30, the CPU 91 performs processing for expanding the received print job (PDL data) into image data (raster data), and then processing for storing the generated image data in the image memory 94 is performed.
Note that the data transmitted from the personal computer 150 includes additional information such as the print job transmission date and time and user name in addition to the print job. The CPU 91 stores the additional information in the additional information memory 110. The processing to be performed is also performed.

  Following the processing in step 30, this time, the routine proceeds to step 40. In step 40, processing for generating an additional pattern B to be superimposed on the image data is performed. The additional pattern B is an arrangement pattern of dots regularly arranged based on additional information stored in the additional information memory 110.

  The term “regular” as used herein means that the dot arrangement interval is determined in advance so that the additional pattern B can be read from the paper on which the image has been formed. In FIG. 4, a grid indicated by a thick line (hereinafter referred to as a basic grid K) is virtually provided so that dots are attached to the intersections of the grids. As a result, the reading device detects the presence or absence of the dod at the intersection of the grids with reference to the position where the reference dod (dot attached to the reference point P) is added, thereby adding the additional pattern from the sheet after image formation. B can be read. In the present embodiment, it is determined that no dot is attached to the position of x shown in FIG. 4 (the portion overlapping with the adjacent grid).

  When the generation of the dot arrangement pattern is completed, the process proceeds to step 50 this time. In step 50, the image data is sequentially read from the image memory 94, and a process of superimposing an additional pattern on the read image data is performed by the CPU 91. That is, the CPU 91 generates data in which the additional pattern B is assigned over almost the entire surface of the image forming area of the paper, and this is superimposed on the image data. As will be described later, when the additional pattern B is allocated to the image forming area of the paper, the CPU 91 performs an adjustment process so that the arrangement of the adjacent additional patterns B (distance between the reference points P ′) becomes irregular.

  The image data on which the additional pattern B is superimposed is output to the control unit 97 in step 90, and the control unit 97 controls the image forming unit 9 and each device in accordance with this.

  Accordingly, a series of image forming processes is started by driving a motor (not shown) as a drive source. That is, the conveyance of the paper 5 is started and laser light is irradiated at a predetermined timing, whereby an electrostatic latent image is formed on the surface of the belt photoreceptor 33 according to the image data on which the additional pattern is superimposed. Is done. Thereafter, a visible image obtained by developing the electrostatic latent image through the developing roller 37 is formed on the belt photoreceptor 33, and this is transferred to the intermediate transfer belt 51.

  By sequentially repeating this for each toner color, a color image including an additional pattern is formed on the intermediate transfer belt 51. The formed color image is then transferred onto the paper 5 by the transfer roller 27 when the paper 5 passes the image forming position. Thereafter, the color image is thermally fixed by passing through the fixing unit 29, and the sheet 5 is discharged onto a discharge tray 69 formed on the upper portion of the main body casing 3 by a discharge roller 67.

4). Processing for Assigning Additional Pattern B to Image Forming Area In this embodiment, as shown in FIG. 4, a coordinate system (main scanning) in which the position of the left corner of the area is the origin (0, 0) in the image forming area of the paper. (Orthogonal coordinate system in which the direction is the X direction and the sub-scanning direction is the Y direction) is assigned, and according to the coordinate system, the arrangement of each dot constituting the additional pattern B is determined, whereby the additional pattern is formed on the image forming area. B is assigned. In the following description, the arrangement in the X direction of the additional pattern B is a column, and the arrangement in the Y direction is a column. The main scanning direction is the scanning direction of laser light, and the sub-scanning direction is the recording medium feeding direction.

  First, the general flow of the allocation of the additional pattern B will be briefly described. The allocation is performed in the column order for each stage. That is, first, the first row (first row in the Y direction) is assigned in order from the first column, and when the assignment process is completed for all the first row, this time, the next stage (second row in the Y direction) is moved. Then, the assignment is performed in the order of the columns in the manner described above, and then the process proceeds to the next stage. By performing this for all stages, the additional pattern B is assigned to the entire image forming area of the paper.

  Now, a specific assignment process will be described with reference to FIG. 5. First, the CPU 91 performs a process of setting the coordinates of the reference point P in the coordinate system of the image forming area. That is, in step 51, the Y coordinate of the reference point P is set to zero (PosY = 0), and subsequently, in step 53, the X coordinate of the reference point is set to zero (PosX = 0). Thereby, the reference point P is set at the position of coordinates (0, 0) shown in FIG.

  When the reference point P is set at the position of coordinates (0, 0), the process proceeds to step 55, where two values Qh and Qv are determined by random numbers. Specifically, Qh is a positive number and is determined within a range of 1/2 or less of the lattice width a, and Qv is a positive number and is 1/2 or less of the lattice width b. It is determined within the range.

  Qh determined in the above manner is the amount of movement of the reference point P in the X direction, and Qv is the amount of movement of the reference point P in the Y direction. Further, the moving direction of the reference point P is determined as follows. That is, for the X direction, the direction toward the right side of FIG. 4 is the positive direction, and for the Y direction, the direction toward the lower side of FIG. 4 is the positive direction. Here, as described above, Qh and Qv are indefinite because the magnitude of the value itself is determined by a random number, but the random number extraction range is limited to a positive value. , Y direction is set in advance so as to move in the positive direction.

  With this configuration, “the movement direction of the reference point when performing the adjustment is unified in one direction in both the X direction and the Y direction” of the present invention is realized.

In step 57, the CPU 91 performs processing for adding the values of Qh and Qv determined in step 55 to the coordinate value of the reference point P and moving the position of the reference point P by the following equations (1) and (2 ).
X coordinate of P ′ = PosX + Qh (1)
Y coordinate of P ′ = PosY + Qv (2)
“P ′” indicates the reference point P after movement.
Here, since PosX = 0 and PosY = 0, the coordinates of P ′ are (Qh, Qv).

  Then, a basic grid K is assigned based on the coordinates (Qh, Qv) of the point P ′. The basic lattice K is a 4 × 4 lattice as shown in FIG. 6, and the specific configuration is as follows. That is, the lattice width is a in the X direction, and the number of lattices is 4 (corresponding to c of the present invention). On the other hand, in the Y direction, the lattice width is b, and the number of lattices is 4 (corresponding to d of the present invention). The overall size of the basic lattice K is such that the width in the X direction is Lh (corresponding to 4a in the expression of the present invention) and the width in the Y direction is Lv (corresponding to 4b in the expression of the present invention).

  Then, as shown in FIG. 6, the CPU 91 determines the coordinate values of the respective dods so that the respective dodds D1 to D4 are positioned at the lattice intersection positions on the basic lattice K. Thereby, the allocation is completed for the additional pattern B11 in the first column in the first stage. In FIG. 6, a grid having the same size as the basic grid arranged in the X direction and the Y direction based on the coordinates (0, 0) is shown by a one-dot chain line. As described above, by performing the process of moving the reference point from the position of the point P to the position of the point P ′, the entire additional pattern B11 is displaced from the position of the one-dot chain line.

  Thus, when the process of allocating the additional pattern B11 in the first column is completed, the CPU 91 performs a process of allocating the additional pattern B in the next column adjacent in the X direction.

That is, the process goes to step 59, and the CPU 91 performs processing for updating the X coordinate of the reference point P in accordance with the coordinate of the next column according to the following equation (3).
PosX = PosX + Lh (3)
Since the original coordinate value of the reference point P is (0, 0), the coordinate of the updated reference point P is (Lh, 0) (see FIG. 7).

  Then, following the completion of the process of step 59, the process proceeds to step 81. In step 81, the CPU 91 determines whether or not the allocation of the additional pattern B has been completed for all columns. Here, since only the first column has been assigned, No is determined, and the process proceeds to step 55.

  In step 55, movement amounts (Qh, Qv) in the X and Y directions are newly determined by random numbers. Thereafter, in step 57, processing for moving the reference point P is performed according to the above equations (1) and (2). Here, since the coordinates of the reference point P are (Lh, 0), the coordinates of the point P ′ are (Lh + Qh, Qv).

  Then, as shown in FIG. 7, the basic grid K is assigned based on the coordinates (Lh + Qh, Qv) of the point P ′, and the respective dodds D1 to D4 are positioned at the grid crossing positions on the basic grid K. The coordinate value of the dodd is determined by the CPU 91. Thereby, the allocation is completed for the additional pattern B21 in the second column.

  Thereafter, the process proceeds to step 59, where the CPU 91 performs again the process of updating the coordinates of the reference point P in accordance with the next column, and the allocation process is performed for the additional pattern B31 in the third column as described above. Then, when the allocation of the additional pattern B is completed for all the columns, Yes is determined in step 81 and the process proceeds to step 83.

In step 83, the CPU 91 performs a process of updating the Y coordinate of the reference point P according to the coordinates of the next stage based on the following equation (4).
PosY = PosY + Lv (4)
Here, since the original value of the Y coordinate of the reference point P is zero (PosY = 0), the updated value is Lv (PosY = Lv). Then, after proceeding to Step 85 and making a No determination, in Step 53, the X coordinate of the reference point P is set to zero.

  Thus, the coordinates of the reference point P are (0, Lv). Thereafter, in step 55, the movement amount (Qh, Qv) of the reference point P is again determined randomly by a random number. Thereafter, in step 57, the CPU 91 performs a process of moving the reference point P in accordance with the above equations (1) and (2).

  Here, since the coordinates of the reference point P are (0, Lv), the coordinates of the point P ′ are (Qh, Lv + Qv). Then, based on the coordinates (Qh, Lv + Qv) of the point P ′, the basic grid K is assigned, and the coordinate values of the respective dods are set by the CPU 91 so that the respective dodds D1 to D4 are positioned at the grid intersection positions on the basic grid K. It is determined. Thereby, the allocation is completed for the additional pattern B12 in the first row in the second row.

  Thereafter, the CPU 91 performs processing for assigning the additional pattern B in the order of B22 and B32 in the same manner as in the first stage. When the allocation of the additional pattern B is completed for all the columns, the CPU 91 makes a Yes determination in step 81 and proceeds to step 83.

  In step 83, the Y coordinate of the reference point P is updated again in accordance with the coordinates of the next stage. As a result, the CPU 91 performs the process of assigning the additional pattern B for the third stage. When the allocation of the additional pattern B is completed for all stages, the CPU 91 makes a Yes determination in step 85, and the process ends.

  At this time, the additional pattern B is assigned over the entire image forming area of the paper, but the processing of step 55 is performed for each additional pattern B, and the movement amount of the reference point P ( Since Qh and Qv) are determined by random numbers, the arrangement of the additional pattern B becomes irregular as shown in FIG. The “adjustment so that the distance between the adjacent reference points (P ′) becomes irregular” of the present invention is realized by the processing of step 55 and step 57. The CPU 91 corresponds to an example of the “adjustment unit” in the present invention.

  In this way, if the arrangement of the additional pattern B is irregular, it is possible to avoid the situation that any additional pattern B is difficult to read due to the overlap with the image, and to improve the probability of reading the additional pattern B. I can do it.

  In addition, the movement of the reference point P follows the values of “Qh” and “Qv”. In the present embodiment, the value of “Qh” is determined within a range of 1/2 of the grid width a, and “Qv” Is also determined within a range of 1/2 of the lattice width b. Moreover, the moving direction is unified in one direction (positive direction). With such a configuration, as shown in FIG. 9, even when the adjacent additional patterns B partially overlap with each other as the reference point P moves (hatching area shown in FIG. 9), the overlapping amount is It is suppressed to half or less of the lattice width a or b. With such a configuration, “the adjustment unit performs the adjustment within a range in which the overlap between adjacent basic lattices is less than a in the X direction and less than b in the Y direction” is realized.

  In this way, by suppressing the overlap between the additional patterns B to less than half of the lattice width, adjacent dots of the additional pattern B (for example, a pair of Da and Db and a pair of Dc and Dd) are continuous. There is no overlap. Specifically, in the present embodiment, the relationship between the dot size and the grid width is set so that eight dots can be added between the grid widths. Therefore, when focusing only on the X direction, as shown in FIG. 10, even if the overlap between the additional patterns B is in the upper limit (half the lattice width), between the dots (between Da and Db), A space for 3 dods can be secured (middle of FIG. 10).

  If the dots are continuous or overlapped between the adjacent additional patterns B, the reading device may erroneously recognize the additional pattern B when reading the additional pattern B. In addition, if the overlap between the additional patterns B is suppressed to half or less of the grid width, a gap can be always secured between adjacent dots, and such a problem can be avoided in advance.

  The lower part of FIG. 10 shows an example in which the overlap between the additional patterns B is increased within a range not exceeding the lattice width a and the space between adjacent dots is reduced. In this manner, in principle, reading is possible if a space of at least one dot is provided between adjacent dots (here, Da and Db).

  Further, in the present embodiment, the movement direction of the reference point P is unified in one direction (positive direction) in both the X direction and the Y direction, but this brings about the following effects. If the movement direction is not standardized and movement is possible in each of the two directions (for example, a configuration in which movement in the negative direction in addition to the positive direction is possible in the X direction), the distance between the previous dodds Also in the case of ensuring the above, it is necessary to perform an arithmetic processing considering two directions, and the processing becomes complicated. In this regard, in the present embodiment, since the movement direction is unified in one direction, the gap necessary for reading the dodd is simply set by setting the upper limit value of the movement amount of the reference point P to half the grid width. , Can be secured between adjacent dods.

  Further, in the present embodiment, the additional pattern B is randomly arranged, but the arrangement itself is a state in which the lattices of the adjacent additional pattern B are aligned in a line without any gap (the reference of the adjacent specific pattern of the present invention). The distance between the points in the X direction is ac and the distance in the Y direction is bd) is a basic arrangement (indicated by a one-dot chain line in FIGS. 6 and 7), and is determined by a random number based on the basic arrangement. The position of the additional pattern B is shifted by the amount of movement (Qh, Qv). With such a configuration, a larger number of additional patterns B can be added on a sheet as a recording medium. Therefore, the probability that the additional pattern B can be read from the paper after image formation is increased.

<Embodiment 2>
Next, a second embodiment of the present invention will be described with reference to FIGS.
As a result of randomizing the arrangement of the additional pattern B in the first embodiment, a state in which the adjacent additional patterns B partially overlap as shown in FIG. 8 may occur. The arrangement is made random and adjacent additional patterns B are not overlapped with each other (an example of the invention described in claim 5, see FIG. 11), and other configurations are the same as in the first embodiment. .

  The flowchart in FIG. 12 corresponds to the flowchart in FIG. 5, but the major difference from the process in the flowchart in FIG. 5 is that the coordinates of the reference point P are updated in accordance with the next stage or the next column. In this case, the movement amount of the adjacent additional pattern B that has already been allocated is considered. In this embodiment, n buffers 1 to n are provided corresponding to the additional patterns of n columns. In each of these buffers, the movement amount Qv of the reference point P in the Y direction in the same row is cumulatively stored during the following process (see FIG. 13).

  Now, specific processing will be described. First, in steps 61 and 63, processing for setting the coordinates of the reference point P of the additional pattern B in the coordinate system of the image forming area is performed. (Same as Embodiment 1). That is, in step 61, the Y coordinate of the reference point P is set to zero (PosY = 0), and subsequently, in step 63, the X coordinate of the reference point is set to zero (PosX = 0). Thereby, the reference point P is set at the position of the coordinates (0, 0).

  In step 61, together with the setting of the coordinate values, a process of clearing (zeroing) the values of all buffers 1 to n is performed. In step 63, the value of # is set to 1. The value of # corresponds to the buffer column number.

When the coordinates of the reference point P are set, the process proceeds to step 65, where the accumulated value (accumulated value of the movement amount Qv) BF stored in the buffer is added to the Y coordinate of the reference point P. Processing is performed according to the following equation (5).
PosY ′ = PosY + BF # (5)
Here, since # = 1 and the accumulated value BF1 = 0, the Y coordinate of the reference point does not change before and after the addition, and PosY ′ = PosY = 0.

  Then, following the process of step 65, the process proceeds to step 67, where two values Qh11 and Qv11 are determined by random numbers. The process in step 67 is the same as the process in step 55 of the first embodiment.

Subsequently, the routine proceeds to step 69. In step 69, a process of moving the position of the reference point P according to the following equation is performed.
X coordinate of P ′ = PosX + Qh (6)
Y coordinate of P ′ = PosY ′ + Qv (7)
“P ′” indicates the reference point P after movement.

  After that, as shown in FIG. 14, the dots constituting the additional pattern B are assigned with reference to the coordinates (Qh11, Qv11) of the point P '. Thereby, the process of assigning the first additional pattern B11 in the first stage is completed.

In step 71, the process of updating the buffer value is performed according to the following equation (8).
BF # = BF # + Qv (8)
Here, since # = 1, the value of the buffer 1 in the first column is updated based on the above equation. That is, since the value of BF1 before update is zero, the value of BF1 after update is Qv11 (see also FIG. 13). When the process of updating the buffer is completed, the process proceeds to step 73 where the value of # is incremented (in this case, from 1 to 2).

In step 75, the process of updating the X coordinate of the reference point P in accordance with the coordinate of the next column is performed according to the following equation (9).
PosX = PosX + Lh + Qh (9)
Here, the value of the X coordinate (PosX) of the reference point P before the update is zero. Therefore, after the update, the value of Lh + Qh11 is added to the original value, so that the value of the X coordinate (PosX) of the reference point P becomes Lh + Qh11.

  Subsequently, although a determination process is performed in step 81, since the determination is NO here, the process proceeds to step 65 again. In step 65, a process of adding the cumulative value BF2 to the Y coordinate of the reference point P based on the above equation (5) is performed. Here, since the cumulative value BF2 = 0, the Y coordinate of the reference point does not change before and after the addition, and PosY ′ = PosY = 0.

  Thus, the coordinates of the reference point P are (Lh + Qh11, 0). As described above, when the X coordinate is updated in step 75 according to the coordinates of the next column, by adding Qh, as shown in FIG. 14, the position of the reference point P becomes H2 shown in FIG. The position H2 ′ is shifted in the positive direction by the movement amount Qh11 of the additional pattern B11 with respect to the position shown in FIG.

  Next, the values of Qh21 and Qv21 are determined by random numbers in step 67, and the process of moving the reference point P in step 69 is performed according to the above equations (6) and (7). Then, the process of assigning the additional pattern B21 is performed based on the position of P ′ after the movement. However, since the moving direction of the reference point P is limited to the positive direction, the additional pattern B21 is H2 ′ shown in FIG. It is moved further to the right than the position of. Therefore, when the additional pattern B21 is assigned, a gap (here, Qh21) corresponding to the movement amount is formed between the additional pattern B11 adjacent in the X direction.

  Thereafter, the above-described series of processing is repeatedly performed until Yes is determined in step 81, and the additional patterns B are sequentially allocated on the image forming area of the sheet without overlapping the adjacent additional patterns B. . Further, as a result of the buffer value being updated in the course of the series of processes described above, as shown in the upper part of FIG. 13, the movement amount Qv of the corresponding additional pattern B in the Y direction is stored in the buffer of each column. Will be stored respectively.

When all the columns and the allocation are completed for the first additional pattern B, Yes is determined in step 81 and the process proceeds to step 83. In step 83, a process of updating the Y coordinate of the reference point P according to the following equation (10) according to the coordinates of the next stage is performed.
PosY = PosY + Lv (10)
Since the Y coordinate of the reference point P is zero before the update, the value of the Y coordinate (PosY) of the reference point P is Lv after the update.

  Thereafter, No is determined in the determination process of step 85, and the process proceeds to step 63 again. In step 63, the value of the X coordinate (PosX) of the reference point P is reset to zero.

Thereafter, in step 65, the process of adding the accumulated value BF # of the movement amount Qv to the Y coordinate of the reference point P is performed according to the above equation (5).
Here, since the accumulated value BF1 = Qv11, the Y coordinate (PosY ′) of the reference point after the addition is Lv + Qv11.

  Thus, the coordinates of the reference point P are (0, Lv + Qv11). In this way, by adding the values stored in the buffer in step 65, as shown in FIG. 15, the position of the reference point P is the amount of movement Qv11 of the additional pattern B11 with respect to the position indicated by V2, The position V2 ′ is shifted in the positive direction (downward in FIG. 15).

  Next, the movement amount (Qh12, Qv12) of the reference point P is determined by a random number at step 67, and the process of moving the reference point P at step 69 is performed according to the above equations (6) and (7). Then, the process of assigning the additional pattern B12 is performed based on the position of P ′ after the movement. However, since the moving direction of the reference point P is limited to the positive direction, the additional pattern B12 is represented by V2 ′ shown in FIG. It will be moved further downward than the position. Accordingly, when the additional pattern B12 is assigned, a gap (here, Qv12) corresponding to the movement amount is formed between the adjacent additional pattern B11.

  Thereafter, the above-described series of processing is repeatedly performed until a Yes determination is made at step 81. As a result, the second-stage additional pattern B is sequentially allocated without overlapping the first-stage additional pattern B adjacent in the Y direction. Since the X coordinate of the reference point P of each additional pattern B22,... Bn2 is determined according to the procedure described in the processing of the first stage additional pattern, adjacent additional patterns B may overlap in the X direction. Absent.

  Further, in the course of performing the series of processes described above, the process of step 71 is executed, and the buffer value is updated according to the above equation (8). As a result, as shown in FIG. When completed, the second-stage movement amount Qv2 is cumulatively added to the first-stage movement amount Qv1 in each of the buffers 1 to n.

  Then, after the allocation of the additional pattern B for the second stage is completed, a process for allocating the additional pattern B of the third stage is performed. At this time, in step 65, according to the above equation (5), The cumulative value BF of the movement amount Qv is added to the Y coordinate (PosY) of the reference point P. Accordingly, the Y coordinate of the reference point P is shifted by the accumulated value of the movement amount Qv of the additional pattern B in the same row located in the upper row. Accordingly, the additional pattern B in the third stage and the subsequent stages is also allocated without overlapping with the upper side additional pattern B adjacent in the Y direction.

  Then, when the allocation process of the additional pattern B is completed for all stages, Yes is determined in step 85, and the process is completed. Note that the CPU 91 performs all of the processing from step 61 to step 85.

  As described above, in the second embodiment, the additional patterns B are arranged at random, but are adjusted so that the adjacent additional patterns B do not overlap each other. Therefore, since the distance between the dods constituting each additional pattern B can be kept in an optimum state, it is possible to read the additional pattern B from the paper after image formation more reliably.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention, and further, within the scope not departing from the gist of the invention other than the following. Various modifications can be made.

  (1) In Embodiment 1 and Embodiment 2, the basic lattice K is a 4 × 4 lattice, but the lattice is not limited to this. In other words, it may be readable by the reading device, and may be rectangular, for example.

  (2) In the first and second embodiments, an electrophotographic laser printer is exemplified as the image forming apparatus, but the present invention can also be applied to an inkjet method.

  (3) In the first and second embodiments, the movement direction of the reference point P is unified to the positive direction in both the X direction and the Y direction. However, the movement direction is not limited to this, and at least the X direction. , Y direction may be unified in one direction. For example, the X direction and the Y direction are both unified in the negative direction, or the X direction is unified in the positive direction, and the Y direction is unified in the negative direction.

FIG. 3 is a side sectional view of a main part of the laser printer according to the first embodiment. Block diagram conceptually showing the electrical configuration of the laser printer Flowchart diagram showing the flow of print processing The figure which shows an example of an additional pattern The flowchart figure which shows the flow of the process which allocates an additional pattern The enlarged view which shows the allocation position of additional pattern B11 Enlarged view showing the allocation position of other additional patterns The figure which shows the state by which the additional pattern was arrange | positioned at random on the image formation area of paper The figure which shows the state where additional patterns overlap Diagram showing gaps between dots FIG. 9 is a diagram illustrating a state in which an additional pattern is allocated on an image forming area of a sheet in the second embodiment. The flowchart figure which shows the flow of the process which allocates an additional pattern The figure which shows accumulation holding | maintenance of the movement amount Qv by a buffer The figure which shows the setting method of the reference point P (P ') about a X direction The figure which shows how to set the reference point P (P ') in the Y direction

Explanation of symbols

1. Laser printer (image forming device)
90 ... control device 91 ... CPU (adjustment means)
B ... Additional pattern (specific pattern)

Claims (5)

In an image forming apparatus for outputting a specific pattern in which a plurality of dots are regularly arranged based on a reference point, and adding a plurality of specific patterns to an image to be formed,
An image forming apparatus, comprising: an adjusting unit configured to adjust a distance between adjacent reference points to be irregular. In the specific pattern, the plurality of dots are regularly arranged on a basic lattice in which the lattice width is a and the number of lattices is c in the X direction, the lattice width is b and the number of lattices is d in the Y direction. It is assumed that the arrangement is arranged,
2. The image forming apparatus according to claim 1, wherein the adjustment unit performs the adjustment within a range in which an overlap between adjacent basic lattices is less than a in the X direction and less than b in the y direction. The adjusting means includes
When the product of a and c is ac and the product of b and d is bd,
3. A relationship in which a distance in the X direction between adjacent reference points of specific patterns is ac and a distance in the Y direction is bd is a basic arrangement, and the adjustment is performed based on the basic arrangement. The image forming apparatus described in 1. 4. The image forming apparatus according to claim 2, wherein a moving direction of the reference point when performing the adjustment is unified in one direction in both the X direction and the Y direction. 5. The adjusting means performs the adjustment,
The distance between a dod constituting one specific pattern and a dod constituting another specific pattern adjacent to the specific pattern is at least a in the X direction and b or more in the Y direction. The image forming apparatus according to claim 2.

Images