JP2008055729A - Method for computing correction amount, correction amount computing device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compute a correction amount necessary for obtaining a correction value of a medium in a material different from a medium of which the correction value is stored in a memory, by using a correction value of another medium. <P>SOLUTION: This method for computing a correction amount comprises a step for obtaining a plurality of conveyance errors correlated to relative positions between a medium and a head, each conveyance error being with respect to a targeting conveyance amount at a time when conveying a prescribed kind of medium, a step of obtaining a plurality of conveyance errors correlated to the relative positions, each conveyance error being with respect to a targeting conveyance amount at a time when conveying the other kind of medium different from the prescribed kind, and a step of computing a correction amount for obtaining a correction value corresponding to the conveyance error of the prescribed kind of the medium by adding it to a correction value corresponding to the conveyance error of the other kind of medium, the correction amount being for obtaining the correction value for correcting the targeting conveyance amount at a time when conveying the prescribed kind of medium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a correction amount calculation method, a correction amount calculation device, and a program.

  An ink jet printer is known as a recording apparatus that transports a medium (for example, paper or cloth) in the transport direction and performs recording on the medium by a head. In such a recording apparatus, if a conveyance error occurs when the medium is conveyed, the head cannot be recorded at a correct position on the medium. In particular, in an ink jet printer, if ink droplets do not land at the correct position on a medium, white stripes and black stripes may occur in the printed image, and the image quality may deteriorate.

Therefore, a method for correcting the transport amount of the medium has been proposed. For example, Patent Document 1 proposes printing a test pattern, reading the test pattern, calculating a correction value based on the read result, and correcting the carry amount based on the correction value when recording an image. Yes.
JP-A-5-96796 JP 2003-11345 A

  By the way, in order to correct the transport amount at each position of the medium, it is necessary to store correction values corresponding to the respective positions of the medium of the respective materials. However, there are cases in which correction values corresponding to the material of all the media cannot be stored due to memory capacity limitations.

  In this way, even when transport is performed for a type of medium that could not be stored in the memory, correction of the transport amount is performed using correction values for other types of media stored in the memory. In some cases, high conveyance accuracy can be obtained. In this case, the correction value corresponding to the type of medium not stored in the memory is obtained based on the correction value of the other type of medium stored in the memory and the predetermined correction amount. Therefore, it is necessary to obtain a predetermined correction amount used when obtaining a correction amount of a medium of a type not stored in the memory using a correction value of another type of medium stored in the memory.

  The present invention has been made in view of such circumstances, and the correction value of a medium having a different material from the medium in which the correction value is stored by using the correction value of another medium in which the correction value is stored. The purpose is to determine the amount of correction required when determining.

The main invention for achieving the above object is:
Obtaining a plurality of transport errors corresponding to the target transport amount when transporting a predetermined type of medium and corresponding to the relative positions of the medium and a head for recording on the medium;
A plurality of transport errors corresponding to a target transport amount when transporting another type of medium different from the predetermined type, and a plurality of transport errors associated with the relative position;
A correction amount for obtaining a correction value for correcting a target transport amount when transporting the predetermined type of medium, which is added to a correction value corresponding to a transport error of the other type of medium and the predetermined amount Calculating a correction amount for obtaining a correction value corresponding to a transport error of a type of medium based on the transport error of the predetermined type of medium and the transport error of the other type of medium;
Is a correction amount calculation method including

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

Obtaining a plurality of transport errors corresponding to the target transport amount when transporting a predetermined type of medium and corresponding to the relative positions of the medium and a head for recording on the medium;
A plurality of transport errors corresponding to a target transport amount when transporting another type of medium different from the predetermined type, and a plurality of transport errors associated with the relative position;
A correction amount for obtaining a correction value for correcting a target transport amount when transporting the predetermined type of medium, which is added to a correction value corresponding to a transport error of the other type of medium and the predetermined amount Calculating a correction amount for obtaining a correction value corresponding to a transport error of a type of medium based on the transport error of the predetermined type of medium and the transport error of the other type of medium;
Correction amount calculation method including
In this way, the correction amount required when the correction value of a medium of a different material from that of the medium storing the correction value is obtained using the correction value of another medium storing the correction value. Can be sought.

In this correction amount calculation method, the correction amount is obtained by calculating an average value of correction values of the predetermined type medium determined based on a conveyance error of the predetermined type medium and the other types of medium. It is desirable that the difference is an average value of correction values of the other types of media obtained based on the transport error. In addition, the medium has a predetermined size, and based on a variation amount of a conveyance error of the medium having the predetermined size, a plurality of correction values of the medium having the predetermined size are used to calculate other values. It is preferable that the method further includes a step of determining a correction value for correcting a target transport amount when transporting a medium having a size. The step of determining the correction value when the size of the other size medium in the transport direction is smaller than the medium of the predetermined size is the relative position when the variation amount of the transport error is small. Preferably, the method includes a step of determining a correction value for correcting a target transport amount when transporting the medium having the other size so that a continuous correction value corresponding to the above is not used. The step of determining the correction value when the size of the other size medium in the transport direction is larger than that of the predetermined size medium is the relative position when the variation amount of the transport error is small. The method may include a step of determining a correction value for correcting the target transport amount when transporting the medium having the other size so that a part of the continuous correction value corresponding to is used a plurality of times.
In this way, the correction amount required when the correction value of a medium of a different material from that of the medium storing the correction value is obtained using the correction value of another medium storing the correction value. Can be sought.

Memory,
A plurality of transport errors corresponding to the relative positions of the medium and a head for recording on the medium, which are transport errors with respect to a target transport amount when transporting a predetermined type of medium;
A memory for storing a plurality of transport errors corresponding to a target transport amount when transporting another type of medium different from the predetermined type, and a transport error associated with the relative position;
An arithmetic unit,
A correction amount for obtaining a correction value for correcting a target transport amount when transporting the predetermined type of medium, which is added to a correction value corresponding to a transport error of the other type of medium and the predetermined amount An arithmetic unit that calculates a correction amount for obtaining a correction value corresponding to a transport error of a type of medium based on the transport error of the predetermined type of medium and the transport error of the other type of medium;
A correction amount calculation device comprising:
In this way, the correction amount required when the correction value of a medium of a different material from that of the medium storing the correction value is obtained using the correction value of another medium storing the correction value. Can be sought.

A program for operating the correction amount calculation device,
Obtaining a plurality of transport errors corresponding to the target transport amount when transporting a predetermined type of medium and corresponding to the relative positions of the medium and a head for recording on the medium;
A plurality of transport errors corresponding to a target transport amount when transporting another type of medium different from the predetermined type, and a plurality of transport errors associated with the relative position;
A correction amount for obtaining a correction value for correcting a target transport amount when transporting the predetermined type of medium, which is added to a correction value corresponding to a transport error of the other type of medium and the predetermined amount Calculating a correction amount for obtaining a correction value corresponding to a transport error of a type of medium based on the transport error of the predetermined type of medium and the transport error of the other type of medium;
A program for causing the correction amount calculation apparatus to execute
In this way, the correction amount required when the correction value of a medium of a different material from that of the medium storing the correction value is obtained using the correction value of another medium storing the correction value. Can be sought.

=== Configuration of Printer ===
<Inkjet printer configuration>
FIG. 1 is a block diagram of the overall configuration of the printer 1. FIG. 2A is a schematic diagram of the overall configuration of the printer 1. FIG. 2B is a cross-sectional view of the overall configuration of the printer 1. Hereinafter, a basic configuration of the printer will be described.

  The printer 1 includes a transport unit 20, a carriage unit 30, a head unit 40, a detector group 50, and a controller 60. The printer 1 that has received print data from the computer 110, which is an external device, controls each unit (the conveyance unit 20, the carriage unit 30, and the head unit 40) by the controller 60. The controller 60 controls each unit based on the print data received from the computer 110 and prints an image on paper. The situation in the printer 1 is monitored by a detector group 50, and the detector group 50 outputs a detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the detector group 50.

  The transport unit 20 is for transporting a medium (for example, paper S) in a predetermined direction (hereinafter referred to as a transport direction). The transport unit 20 includes a paper feed roller 21, a transport motor 22 (also referred to as a PF motor), a transport roller 23, a platen 24, and a paper discharge roller 25. The paper feed roller 21 is a roller for feeding the paper inserted into the paper insertion slot into the printer. The transport roller 23 is a roller that transports the paper S fed by the paper feed roller 21 to a printable area, and is driven by the transport motor 22. The platen 24 supports the paper S being printed. The paper discharge roller 25 is a roller for discharging the paper S to the outside of the printer, and is provided on the downstream side in the transport direction with respect to the printable area. The paper discharge roller 25 rotates in synchronization with the transport roller 23.

  When the transport roller 23 transports the paper S, the paper S is sandwiched between the transport roller 23 and the driven roller 26. Thereby, the posture of the paper S is stabilized. On the other hand, when the paper discharge roller 25 transports the paper S, the paper S is sandwiched between the paper discharge roller 25 and the driven roller 27. Since the discharge roller 25 is provided on the downstream side in the transport direction from the printing area, the driven roller 27 is configured so that the contact surface with the paper S is small (see also FIG. 4). For this reason, when the lower end of the paper S passes through the transport roller 23 and the paper S is transported only by the paper discharge roller 25, the posture of the paper S is likely to be unstable and the transport characteristics are also likely to change.

  The carriage unit 30 is for moving (also referred to as “scanning”) the head in a predetermined direction (hereinafter referred to as a moving direction). The carriage unit 30 includes a carriage 31 and a carriage motor 32 (also referred to as a CR motor). The carriage 31 can reciprocate in the moving direction and is driven by a carriage motor 32. Further, the carriage 31 detachably holds an ink cartridge that stores ink.

  The head unit 40 is for ejecting ink onto paper. The head unit 40 includes a head 41 having a plurality of nozzles. Since the head 41 is provided on the carriage 31, when the carriage 31 moves in the movement direction, the head 41 also moves in the movement direction. Then, by intermittently ejecting ink while the head 41 is moving in the moving direction, dot lines (raster lines) along the moving direction are formed on the paper.

  The detector group 50 includes a linear encoder 51, a rotary encoder 52, a paper detection sensor 53, an optical sensor 54, and the like. The linear encoder 51 detects the position of the carriage 31 in the moving direction. The rotary encoder 52 detects the rotation amount of the transport roller 23. The paper detection sensor 53 detects the position of the leading edge of the paper being fed. The optical sensor 54 detects the presence or absence of paper by a light emitting unit and a light receiving unit attached to the carriage 31. The optical sensor 54 can detect the position of the edge of the paper while being moved by the carriage 31 to detect the width of the paper. The optical sensor 54 also detects the leading end (the end on the downstream side in the transport direction, also referred to as the upper end) and the rear end (the end on the upstream side in the transport direction, also referred to as the lower end) depending on the situation. it can.

  The controller 60 is a control unit (control unit) for controlling the printer. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 transmits and receives data between the computer 110 which is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM and an EEPROM. The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63.

<About nozzle>
FIG. 3 is an explanatory diagram showing the arrangement of nozzles on the lower surface of the head 41. On the lower surface of the head 41, a black ink nozzle group K, a cyan ink nozzle group C, a magenta ink nozzle group M, and a yellow ink nozzle group Y are formed. Each nozzle group includes 90 nozzles that are ejection openings for ejecting ink of each color.

  The plurality of nozzles of each nozzle group are aligned at a constant interval (nozzle pitch: k · D) along the transport direction. Here, D is the minimum dot pitch in the carrying direction (that is, the interval at the highest resolution of dots formed on the paper S). K is an integer of 1 or more. For example, when the nozzle pitch is 90 dpi (1/90 inch) and the dot pitch in the transport direction is 720 dpi (1/720 inch), k = 8.

The nozzles in each nozzle group are assigned a smaller number as the nozzles on the downstream side (# 1 to # 90). That is, the nozzle # 1 is located downstream of the nozzle # 90 in the transport direction. It should be noted that the optical sensor 54 described above is located at substantially the same position as the nozzle # 90 on the most upstream side with respect to the position in the paper transport direction.
Each nozzle is provided with an ink chamber (not shown) and a piezoelectric element. By driving the piezo element, the ink chamber expands and contracts, and ink droplets are ejected from the nozzle.

=== Conveying error ===
<Conveying paper>
FIG. 4 is an explanatory diagram of the configuration of the transport unit 20.
The transport unit 20 drives the transport motor 22 by a predetermined drive amount based on a transport command from the controller 60. The conveyance motor 22 generates a driving force in the rotation direction according to the commanded driving amount. The transport motor 22 rotates the transport roller 23 using this driving force. That is, when the transport motor 22 generates a predetermined drive amount, the transport roller 23 rotates by a predetermined rotation amount. When the transport roller 23 rotates with a predetermined rotation amount, the paper is transported with a predetermined transport amount.

The carry amount of the paper is determined according to the rotation amount of the carry roller 23. Here, it is assumed that when the transport roller 23 makes one rotation, the paper is transported by 1 inch (that is, the peripheral length of the transport roller 23 is 1 inch). For this reason, when the transport roller 23 rotates 1/4, the paper is transported by 1/4 inch.
Therefore, if the rotation amount of the conveyance roller 23 can be detected, the conveyance amount of the paper can also be detected. Therefore, a rotary encoder 52 is provided to detect the rotation amount of the transport roller 23.

The rotary encoder 52 includes a scale 521 and a detection unit 522. The scale 521 has a large number of slits provided at predetermined intervals. The scale 521 is provided on the transport roller 23. That is, the scale 521 rotates together when the transport roller 23 rotates. When the transport roller 23 rotates, the slits of the scale 521 sequentially pass through the detection unit 522. The detection unit 522 is provided to face the scale 521 and is fixed to the printer main body side. The rotary encoder 52 outputs a pulse signal each time a slit provided in the scale 521 passes through the detection unit 522. Since the slits provided in the scale 521 sequentially pass through the detection unit 522 according to the rotation amount of the conveyance roller 23, the rotation amount of the conveyance roller 23 is detected based on the output of the rotary encoder 52. When the paper is transported in an amount of 1 inch, the controller 60 drives the transport motor 22 until the rotary encoder 52 detects that the transport roller 23 has rotated once. As described above, the controller 60 drives the carry motor 22 until the rotary encoder 52 detects that the rotation amount is in accordance with the target carry amount (target carry amount), and sets the paper to the target carry amount. Transport.

<About transport error>
By the way, the rotary encoder 52 directly detects the rotation amount of the transport roller 23, and strictly speaking, does not detect the transport amount of the paper S. For this reason, when the rotation amount of the transport roller 23 and the transport amount of the paper S do not match, the rotary encoder 52 cannot accurately detect the transport amount of the paper S, and a transport error (detection error) occurs. There are two types of transport errors: DC component transport errors and AC component transport errors.

  The DC component transport error is a predetermined amount of transport error that occurs when the transport roller rotates once. The DC component transport error is considered to be caused by the circumference of the transport roller 23 being different for each printer due to a manufacturing error or the like. That is, the DC component transport error is a transport error that occurs because the designed peripheral length of the transport roller 23 is different from the actual peripheral length of the transport roller 23. The DC component transport error is constant regardless of the start position when the transport roller 23 rotates once. However, the actual DC component transport error varies depending on the total transport amount of paper due to the influence of paper friction and the like (described later). In other words, the actual DC component transport error varies depending on the relative positional relationship between the paper S and the transport roller 23 (or the paper S and the head 41).

  The AC component transport error is a transport error according to the location of the peripheral surface of the transport roller used during transport. The AC component transport error varies depending on the location of the peripheral surface of the transport roller used during transport. That is, the AC component transport error varies depending on the rotation position of the transport roller at the start of transport and the transport amount.

  FIG. 5 is a graph for explaining the AC component transport error. The horizontal axis represents the rotation amount of the transport roller 23 from the reference rotation position. The vertical axis represents the transport error. If this graph is differentiated, a transport error that occurs when the transport roller is transporting at the rotational position can be derived. Here, the cumulative transport error at the reference position is zero, and the DC component transport error is also zero.

  When the transport roller 23 rotates 1/4 from the reference position, a transport error of δ_90 occurs, and the paper is transported by 1/4 inch + δ_90. However, if the transport roller 23 further rotates by 1/4, a transport error of -δ_90 occurs, and the paper is transported by 1/4 inch -δ_90.

There are three possible causes for the AC component transport error, for example.
First, the influence of the shape of the transport roller can be considered. For example, when the conveyance roller is elliptical or egg-shaped, the distance to the rotation center differs depending on the location of the circumferential surface of the conveyance roller. When the medium is transported at a portion where the distance to the rotation center is long, the transport amount with respect to the rotation amount of the transport roller increases. On the other hand, when the medium is transported at a portion where the distance to the rotation center is short, the transport amount with respect to the rotation amount of the transport roller is reduced.

  Secondly, the eccentricity of the rotation shaft of the transport roller can be considered. Also in this case, the length to the rotation center differs depending on the location of the peripheral surface of the transport roller. For this reason, even if the rotation amount of the conveyance roller is the same, the conveyance amount varies depending on the location of the circumferential surface of the conveyance roller.

  Thirdly, a mismatch between the rotation axis of the transport roller and the center of the scale 521 of the rotary encoder 52 can be considered. In this case, the scale 521 rotates eccentrically. As a result, the amount of rotation of the transport roller 23 with respect to the detected pulse signal differs depending on the location of the scale 521 detected by the detection unit 522. For example, when the detected location of the scale 521 is away from the rotation axis of the conveyance roller 23, the rotation amount of the conveyance roller 23 with respect to the detected pulse signal decreases, and the conveyance amount decreases. On the other hand, when the detected location of the scale 521 is close to the rotation axis of the conveyance roller 23, the rotation amount of the conveyance roller 23 with respect to the detected pulse signal increases, and thus the conveyance amount increases.

  Due to the above cause, the AC component transport error is substantially a sine curve as shown in FIG.

<Conveyance error to be corrected in the reference example>
FIG. 6 is a graph (conceptual diagram) of a transport error that occurs when transporting a paper having a size of 101.6 mm × 152.4 mm (4 inches × 6 inches). The horizontal axis of the graph indicates the total transport amount of paper. The vertical axis of the graph indicates the transport error. The dotted line in the figure is a graph of the DC component transport error. The AC component transport error can be obtained by subtracting the dotted line value (DC component transport error) in the drawing from the solid line value (total transport error) in the diagram. The AC component transport error is almost a sine curve regardless of the total paper transport amount. On the other hand, the DC component transport error indicated by the dotted line differs depending on the total transport amount of paper due to the influence of paper friction and the like.

As already described, the AC component transport error varies depending on the location of the peripheral surface of the transport roller 23. For this reason, even when the same paper is transported, if the rotation position of the transport roller 23 at the start of transport is different, the transport error of the AC component is different, and therefore the total transport error (the transport error indicated by the solid line in the graph). ) Will be different. On the other hand, the DC component transport error is different from the AC component transport error and is not related to the location of the peripheral surface of the transport roller. The transport error (DC component transport error) that occurs when the motor rotates once is the same.
Further, when trying to correct the AC component transport error, the controller 60 needs to detect the rotational position of the transport roller 23. However, in order to detect the rotational position of the transport roller 23, it is necessary to further provide an origin sensor in the rotary encoder 52, which increases costs.
Therefore, in the correction of the carry amount of the reference example described below, the carry error of the DC component is corrected.

  On the other hand, the DC component transport error varies depending on the total transport amount of the paper (in other words, the relative positional relationship between the paper S and the transport roller 23) (see the dotted line in FIG. 6). For this reason, if more correction values can be prepared according to the position in the transport direction, the transport error can be finely corrected. Therefore, in the reference example, a correction value for correcting the DC component transport error is prepared for each 1/4 inch range, not for each 1 inch range corresponding to one rotation of the transport roller 23. .

=== General Description ===
FIG. 7 is a flowchart for determining a correction value for correcting the carry amount. FIG. 8A to FIG. 8C are explanatory diagrams of how the correction value is determined. These processes are performed in the inspection process of the printer manufacturing factory. Prior to this process, the inspector connects the assembled printer 1 to the computer 110 in the factory. A scanner 150 is also connected to the computer 110 in the factory, and a printer driver, a scanner driver, and a correction value acquisition program are installed in advance.

  First, the printer driver transmits print data to the printer 1, and the printer 1 prints the measurement pattern on the test sheet TS (S101, FIG. 8A). Next, the inspector sets the test sheet TS on the scanner 150, and the scanner driver causes the scanner 150 to read the measurement pattern and acquire image data (S102, FIG. 8B). A reference sheet is set in the scanner 150 together with the test sheet TS, and a reference pattern drawn on the reference sheet is also read together.

  Then, the correction value acquisition program analyzes the acquired image data and calculates a correction value (S103). Then, the correction value acquisition program transmits the correction data to the printer 1 and stores the correction value in the memory 63 of the printer 1 (FIG. 8C). The correction value stored in the printer reflects the conveyance characteristics of each printer.

  The printer storing the correction value is packed and delivered to the user. When the user prints an image with the printer, the printer conveys the paper based on the correction value and prints the image on the paper.

=== Printing Pattern for Measurement (S101) ===
First, the measurement pattern printing will be described. Similar to normal printing, the printer 1 alternately repeats a dot formation process for forming dots by ejecting ink from the moving nozzles and a transport operation for transporting the paper in the transport direction, and the measurement pattern is printed on the paper. Print on. In the following description, the dot formation process is referred to as “pass”, and the nth dot formation process is referred to as “pass n”.

  FIG. 9 is an explanatory diagram of how the measurement pattern is printed. The size of the test sheet TS on which the measurement pattern is printed is 101.6 mm × 152.4 mm (4 inches × 6 inches).

  On the right side of the figure, a measurement pattern printed on the test sheet TS is shown. The left rectangle in the drawing indicates the position of the head 41 in each pass (relative position with respect to the test sheet TS). For convenience of explanation, the head 41 is depicted as moving with respect to the test sheet TS, but this figure shows the relative positional relationship between the head and the test sheet TS. The test sheet TS is intermittently conveyed in the conveyance direction.

  When the test sheet TS continues to be conveyed, the lower end of the test sheet TS passes through the conveyance roller 23. The position of the test sheet TS that faces the most upstream nozzle # 90 when the lower end of the test sheet TS passes the transport roller 23 is indicated by a dotted line in the drawing as an “NIP line”. That is, in the path in which the head 41 is above the NIP line in the figure, printing is performed with the test sheet TS sandwiched between the transport roller 23 and the driven roller 26 (also referred to as “NIP state”). Is called. In the drawing, in a path where the head 41 is below the NIP line, there is no test sheet TS between the transport roller 23 and the driven roller 26 (the test sheet TS is formed only by the paper discharge roller 25 and the driven roller 27). And is also referred to as “non-NIP state”).

The measurement pattern includes an identification code and a plurality of lines.
The identification code is an individual identification symbol for identifying each printer 1. This identification code is read together when the measurement pattern is read in S102, and is identified by the computer 110 by character recognition by OCR.
Each line is formed along the moving direction. Many lines are formed on the upper end side of the NIP line. Regarding the line on the upper end side from the NIP line, the i-th line in order from the upper end side is referred to as “Li”. Two lines are formed on the lower end side of the NIP line. Of the two lines on the lower end side of the NIP line, the upper end side line is called Lb1, and the lower end side line (lowermost line) is called Lb2. A specific line is formed longer than the other lines. For example, the line L1, the line L13, and the line Lb2 are formed longer than the other lines. These lines are formed as follows.

  First, after the test sheet TS is conveyed to a predetermined printing start position, ink droplets are ejected from only the nozzle # 90 in pass 1 to form a line L1. After pass 1, the controller 60 rotates the transport roller 23 by 1/4 to transport the test sheet TS by about 1/4 inch. After transport, in pass 2, ink droplets are ejected only from nozzle # 90, and line L2 is formed. Thereafter, the same operation is repeated, and the lines L1 to L20 are formed at intervals of about 1/4 inch. Thus, the lines L1 to L20 located on the upper end side of the NIP line are formed by the most upstream nozzle # 90 among the nozzles # 1 to # 90. Thereby, as many lines as possible can be formed on the test sheet TS in the NIP state. The lines L1 to L20 are formed only by the nozzle # 90, but in the pass for printing the identification code, nozzles other than the nozzle # 90 are also used when printing the identification code.

  After the lower end of the test sheet TS passes through the transport roller 23, ink droplets are ejected only from the nozzle # 90 in pass n to form a line Lb1. After pass 1, the controller 60 rotates the transport roller 23 once to transport the test sheet TS by about 1 inch. After transport, in pass n + 1, ink droplets are ejected only from nozzle # 3 to form line Lb2. If nozzle # 1 is used, the distance between line Lb1 and line Lb2 becomes very narrow (about 1/90 inch), and it becomes difficult to measure the distance between line Lb1 and line Lb2 later. . For this reason, here, by forming the line Lb2 using the nozzle # 3 located upstream in the transport direction from the nozzle # 1, the distance between the line Lb1 and the line Lb2 is widened to facilitate measurement.

  By the way, when the test sheet TS is conveyed ideally, the interval between the lines L1 to L20 should be exactly 1/4 inch. However, if there is a conveyance error, the line interval does not become 1/4 inch. If the test sheet TS is transported more than the ideal transport amount, the line interval increases. Conversely, when the test sheet TS is transported less than the ideal transport amount, the line interval is narrowed. That is, the interval between two lines reflects a transport error in a transport process performed between a path in which one line is formed and a path in which the other line is formed. For this reason, if the distance between two lines is measured, it is possible to measure a transport error in a transport process performed between a path in which one line is formed and a path in which the other line is formed. .

  Similarly, the distance between the line Lb1 and the line Lb2 is such that when the test sheet TS is transported ideally (more precisely, when the ink ejection of the nozzle # 90 and the nozzle # 3 is the same). It should be exactly 3/90 inches. However, if there is a transport error, the line spacing does not become 3/90 inches. For this reason, it is considered that the interval between the line Lb1 and the line Lb2 reflects a transport error in the transport process in the non-NIP state. For this reason, if the distance between the line Lb1 and the line Lb2 is measured, it is possible to measure the transport error in the transport process in the non-NIP state.

=== Reading Pattern (S102) ===
<Scanner configuration>
First, the configuration of the scanner 150 used for reading the measurement pattern will be described.
FIG. 10A is a longitudinal sectional view of the scanner 150. FIG. 10B is a top view of the scanner 150 with the upper lid 151 removed.

  The scanner 150 includes an upper cover 151, a document table glass 152 on which the document 5 is placed, a reading carriage 153 that moves in the sub-scanning direction while facing the document 5 through the document table glass 152, and a sub-scanning of the reading carriage 153. A guide unit 154 for guiding in the direction, a moving mechanism 155 for moving the reading carriage 153, and a scanner controller (not shown) for controlling each unit in the scanner 150 are provided. The reading carriage 153 receives an exposure lamp 157 for irradiating the original 5 with light, a line sensor 158 for detecting a line image in the main scanning direction (a direction perpendicular to the paper surface in FIG. 10A), and reflected light from the original 5. An optical system 159 for guiding to the line sensor 158 is provided. A broken line inside the reading carriage 153 in the drawing indicates a locus of light.

  When reading the image of the document 5, the operator opens the upper cover 151, places the document 5 on the document table glass 152, and closes the upper cover 151. Then, the scanner controller moves the reading carriage 153 along the sub-scanning direction with the exposure lamp 157 emitting light, and reads the image on the surface of the document 5 by the line sensor 158. The scanner controller transmits the read image data to the scanner driver of the computer 110, whereby the computer 110 acquires the image data of the document 5.

<Reading position accuracy>
As will be described later, in the reference example, the scanner 150 reads the measurement pattern of the test sheet TS and the reference pattern of the reference sheet with a resolution of 720 dpi (main scanning direction) × 720 dpi (sub-scanning direction). For this reason, in the following description, description will be made on the assumption that an image is read at a resolution of 720 × 720 dpi.

  FIG. 11 is a graph of the error in the reading position of the scanner. The horizontal axis of the graph indicates the reading position (theoretical value) (that is, the horizontal axis of the graph indicates the position (theoretical value) of the reading carriage 153). The vertical axis of the graph represents the reading position error (difference between the theoretical value of the reading position and the actual reading position). For example, when the reading carriage 153 is moved by 1 inch (= 25.4 mm), an error of about 60 μm occurs.

  If the theoretical value of the reading position matches the actual reading position, a pixel that is 720 pixels away from the pixel indicating the reference position (position where the reading position is zero) in the sub-scanning direction is exactly 1 inch from the reference position. It should show an image at a distant location. However, when an error in the reading position as shown in the graph occurs, a pixel that is 720 pixels away from the pixel that indicates the reference position in the sub-scanning direction is a position that is further 60 μm away from a position that is 1 inch away from the reference position. An image will be shown.

  If the slope of the graph is zero, images should be read at equal intervals every 1/720 inch. However, when the slope of the graph is positive, images are read at intervals longer than 1/720 inch. Further, when the slope of the graph is negative, images are read at intervals shorter than 1/720 inch.

As a result, even if the measurement pattern lines are formed at equal intervals, the line images on the image data do not have equal intervals in a state where there is an error in the reading position. Thus, in the state where there is an error in the reading position, the line position cannot be accurately measured by simply reading the measurement pattern.
Therefore, in the reference example, when the test sheet TS is set and the measurement pattern is read by the scanner, the reference sheet is set and the reference pattern is also read.

<Reading measurement pattern and reference pattern>
FIG. 12A is an explanatory diagram of the reference sheet SS. FIG. 12B is an explanatory diagram showing a state in which the test sheet TS and the reference sheet SS are set on the platen glass 152.
The size of the reference sheet SS is 10 mm × 300 mm, and the reference sheet SS has a long and thin shape. In the reference sheet SS, a large number of lines are formed as reference patterns at intervals of 36 dpi. Since the reference sheet SS is repeatedly used, it is not a paper but a PET film. The reference pattern is formed with high accuracy by laser processing.

  By using a jig (not shown), the test sheet TS and the reference sheet SS are set at predetermined positions on the platen glass 152. The reference sheet SS is set on the platen glass 152 so that the long side thereof is parallel to the sub-scanning direction of the scanner 150, that is, each line of the reference sheet SS is parallel to the main scanning direction of the scanner 150. The A test sheet TS is set next to the reference sheet SS. The test sheet TS is set on the platen glass 152 so that the long side is parallel to the sub-scanning direction of the scanner 150, that is, the lines of the measurement pattern are parallel to the main scanning direction.

  With the test sheet TS and the reference sheet SS set in this way, the scanner 150 reads the measurement pattern and the reference pattern. At this time, due to the influence of the error in the reading position, the image of the measurement pattern in the reading result becomes a distorted image as compared with the actual measurement pattern. Similarly, the image of the reference pattern is also distorted compared to the actual reference pattern.

  Note that the measurement pattern image in the reading result is affected not only by the error of the reading position but also by the conveyance error of the printer 1. On the other hand, since the reference pattern is formed at equal intervals irrespective of the transport error of the printer, the image of the reference pattern is affected by the error in the reading position of the scanner 150. It is not affected by the error.

  Therefore, when calculating the correction value based on the measurement pattern image, the correction value acquisition program cancels the influence of the reading position error in the measurement pattern image based on the reference pattern image.

=== Calculation of Correction Value (S103) ===
Before describing the correction value calculation, the image data acquired from the scanner 150 will be described. The image data is composed of a plurality of pixel data. Each pixel data indicates the gradation value of the corresponding pixel. If the reading error of the scanner is ignored, each pixel corresponds to a size of 1/720 inch × 1/720 inch. An image (digital image) is configured with such a pixel as a minimum structural unit, and the image data is data indicating such an image.

  FIG. 13 is a flowchart of the correction value calculation process in S103. The computer 110 executes each process according to the correction value acquisition program. That is, the correction value acquisition program has a code for causing the computer 110 to execute each process.

<Image Division (S131)>
First, the computer 110 divides the image indicated by the image data acquired from the scanner 150 into two (S131).
FIG. 14 is an explanatory diagram of image division (S131). On the left side of the drawing, an image indicated by the image data acquired from the scanner is drawn. The divided image is drawn on the right side in the figure. In the following description, the left-right direction (horizontal direction) in the figure is called the x direction, and the up-down direction (vertical direction) in the figure is called the y direction. Each line in the reference pattern image is substantially parallel to the x direction, and each line in the measurement pattern image is substantially parallel to the y direction.

  The computer 110 divides the image into two by extracting an image in a predetermined range from the image of the reading result. By dividing the image of the reading result into two, one image shows the image of the reference pattern and the other image shows the image of the measurement pattern. The reason for dividing in this way is that the reference sheet SS and the test sheet TS may be separately inclined and set in the scanner 150, so that the inclination correction (S133) is performed separately.

<Detection of Inclination of Each Image (S132)>
Next, the computer 110 detects the inclination of the image (S132).
FIG. 15A is an explanatory diagram illustrating a state where the inclination of the image of the measurement pattern is detected. The computer 110 extracts, from the image data, the KX2th pixel from the left and the KY1st to JY pixels from the top. Similarly, the computer 110 extracts from the image data the KX3th pixel from the left and the KY1 to JY pixels from the top. The parameters KX2, KX3, KY1, and JY are set so that the pixel indicating the line L1 is included in the extracted pixels.
FIG. 15B is a graph of the gradation values of the extracted pixels. The horizontal axis indicates the position of the pixel (Y coordinate). The vertical axis indicates the gradation value of the pixel. The computer 110 obtains the gravity center positions KY2 and KY3 based on the pixel data of the extracted JY pixels.
Then, the computer 110 calculates the inclination θ of the line L1 by the following equation.
θ = tan ⁻¹ {(KY2-KY3) / (KX2-KX3)}

  The computer 110 detects not only the inclination of the measurement pattern image but also the inclination of the reference pattern image. Since the method of detecting the inclination of the image of the reference pattern is substantially the same as the above method, the description thereof is omitted.

<Correction of inclination of each image (S133)>
Next, the computer 110 rotates the image based on the inclination θ detected in S132 and corrects the inclination of the image (S133). The measurement pattern image is rotationally corrected based on the inclination result of the measurement pattern image, and the reference pattern image is rotationally corrected based on the inclination result of the reference pattern image.
A bilinear method is used as an algorithm for image rotation processing. Since this algorithm is well known, its description is omitted.

<Detection of tilt during printing (S134)>
Next, the computer 110 detects an inclination (skew) during printing of the measurement pattern (S134). If the lower end of the test sheet passes the transport roller when printing the measurement pattern, the lower end of the test sheet may come into contact with the head 41 and the test sheet may move. When this happens, the correction value calculated from the measurement pattern becomes inappropriate. Therefore, it is detected whether or not the lower end of the test sheet is in contact with the head 41 by detecting the inclination at the time of printing the measurement pattern.

  FIG. 16 is an explanatory diagram of how the inclination is detected when the measurement pattern is printed. First, the computer 110 sets the left-side interval YL and the right-side interval YR in the line L1 (the uppermost line) and the line Lb1 (the lowermost line, the line formed after the lower end passes through the transport roller). Is detected. Then, the computer 110 calculates the difference between the interval YL and the interval YR. If the difference is within the predetermined range, the computer 110 proceeds to the next process (S135). If the difference is outside the predetermined range, an error is determined.

<Calculation of margin amount (S135)>
Next, the computer 110 calculates a margin amount (S135).
FIG. 17 is an explanatory diagram of the margin amount X. A solid square (outer square) in the figure indicates an image after the rotation correction in S133. A dotted-line rectangle (inner oblique rectangle) in the figure indicates an image before rotation correction. In order to make the image after rotation correction into a rectangular shape, right-angled triangular margins are added to the four corners of the rotated image when the rotation correction processing of S133 is performed.

If the inclination of the reference sheet SS and the inclination of the test sheet TS are different, the amount of added margin is different, and the position of the measurement pattern line relative to the reference pattern is relative before and after the rotation correction (S133). It will shift to. Therefore, the computer 110 obtains the margin amount X by the following equation, and subtracts the margin amount X from the line position calculated in S136, thereby preventing the shift of the line position of the measurement pattern with respect to the reference pattern.
X = (w cos θ−W ′ / 2) × tan θ

<Calculation of Line Position in Scanner Coordinate System (S136)>
Next, the computer 110 calculates the position of the line of the reference pattern and the position of the line of the measurement pattern in the scanner coordinate system (S136).

  The scanner coordinate system is a coordinate system when the size of one pixel is 1/720 × 1/720 inch. The scanner 150 has a reading position error, and considering the reading position error, the corresponding actual area of each pixel data is not exactly 1/720 inch × 1/720 inch, but in the scanner coordinate system, The size of the corresponding region (pixel) of each pixel data is 1/720 × 1/720 inch. Further, the position of the upper left pixel in each image is set as the origin of the scanner coordinate system.

FIG. 18A is an explanatory diagram of an image range used when calculating the position of a line. Image data of an image in a range indicated by a dotted line in the figure is used when calculating the position of the line. FIG. 18B is an explanatory diagram of calculation of the position of the line. The horizontal axis indicates the position of the pixel in the y direction (scanner coordinate system). The vertical axis indicates the gradation value of the pixel (the average value of the gradation values of the pixels arranged in the x direction).
The computer 110 obtains the position of the peak value of the gradation value and sets a predetermined range centered on this position as the calculation range. Based on the pixel data of the pixels in this calculation range, the barycentric position of the gradation value is calculated, and this barycentric position is set as the line position.

  FIG. 19 is an explanatory diagram of the calculated line positions (note that the positions shown in the figure are made dimensionless by a predetermined calculation). Although the reference pattern is composed of equally spaced lines, the positions of the calculated lines are not evenly spaced when attention is paid to the position of the center of gravity of each line of the reference pattern. This is considered to be due to the influence of the reading position error of the scanner 150.

<Calculation of absolute position of each line of measurement pattern (S137)>
Next, the computer 110 calculates the absolute position of each line of the measurement pattern (S137).
FIG. 20 is an explanatory diagram for calculating the absolute position of the i-th line of the measurement pattern. Here, the i-th line of the measurement pattern is located between the j−1th line of the reference pattern and the j-th line of the reference pattern. In the following description, the position (scanner coordinate system) of the i-th line of the measurement pattern is referred to as “S (i)”, and the position of the j-th line (scanner coordinate system) of the reference pattern is “K (j)”. " The interval between the j−1th line and the jth line of the reference pattern (interval in the y direction) is called “L”, and the j−1th line of the reference pattern and the ith line of the measurement pattern (Interval in the y direction) is referred to as “L (i)”.

First, the computer 110 calculates the ratio H of the interval L (i) to the interval L based on the following equation.
H = L (i) / L
= {S (i) -K (j-1)} / {K (j) -K (j-1)}

By the way, since the actual reference patterns on the reference sheet SS are equally spaced, if the absolute position of the first line of the reference pattern is zero, the position of an arbitrary line of the reference pattern can be calculated. For example, the absolute position of the second line of the reference pattern is 1/36 inch. Therefore, when the absolute position of the jth line of the reference pattern is “J (j)” and the absolute position of the ith line of the measurement pattern is “R (i)”, R ( i) can be calculated.
R (i) = {J (j) −J (j−1)} × H + J (j−1)

Here, a specific procedure for calculating the absolute position of the first line of the measurement pattern in FIG. 19 will be described. First, the computer 110 determines that the first line of the measurement pattern is located between the second line and the third line of the reference pattern based on the value of S (1) (373.768667). To detect. Next, the computer 110 calculates that the ratio H is 0.40143008 (= (373.7686667-309.613250) / (469.430413-309.613250)). Next, the computer 110 calculates that the absolute position R (1) of the first line of the measurement pattern is 0.98878678 mm (= 0.038928613 inch = {1/36 inch} × 0.40143008 + 1/36 inch).
In this way, the computer 110 calculates the absolute position of each line of the measurement pattern.

<Calculation of Correction Value (S138)>
Next, the computer 110 calculates correction values corresponding to a plurality of transport operations performed when the measurement pattern is formed (S138). Each correction value is calculated based on the difference between the theoretical line spacing and the actual line spacing.

  The correction value C (i) of the transport operation performed between the pass i and the pass i + 1 is from “6.35 mm” (1/4 inch, that is, the theoretical distance between the line Li and the line Li + 1) to “R. It is a value obtained by subtracting (i + 1) −R (i) ”(the absolute position of the line Li + 1 and the actual distance between the lines Li). For example, the correction value C (1) of the transport operation performed between pass 1 and pass 2 is 6.35 mm- {R (2) -R (1)}. In this way, the computer 110 calculates the correction value C (1) to the correction value C (19).

  However, when the correction value is calculated using the lines Lb1 and Lb2 below the NIP line (upstream in the transport direction), the theoretical distance between the line Lb1 and the line Lb2 is “0.847 mm” (= 3/90 Calculate as inches. In this way, the computer 110 calculates the correction value Cb in the non-NIP state.

  FIG. 21 is an explanatory diagram of a corresponding range of the correction value C (i). If the value obtained by subtracting the correction value C (1) from the initial target carry amount is set as the target in the carrying operation between pass 1 and pass 2 when the measurement pattern is printed, the actual value is obtained. The transport amount should be exactly 1/4 inch (= 6.35 mm). Similarly, if a value obtained by subtracting the correction value Cb from the original target carry amount is set as the target in the carrying operation between pass n and pass n + 1 when the measurement pattern is printed, the actual value is obtained. The carry amount should be exactly 1 inch.

<Averaging correction values (S139)>
Incidentally, since the rotary encoder 52 of the reference example does not include the origin sensor, the controller 60 can detect the rotation amount of the transport roller 23 but does not detect the rotation position of the transport roller 23. For this reason, the printer 1 cannot guarantee the rotational position of the transport roller 23 at the start of transport. That is, every time printing is performed, the rotational position of the transport roller 23 at the start of transport may be different. On the other hand, the interval between two adjacent ruled lines in the measurement pattern is affected not only by the DC component transport error when transporting at 1/4 inch, but also by the AC component transport error.

  Therefore, when correcting the target carry amount, if the correction value C calculated based on the interval between two ruled lines adjacent to each other in the measurement pattern is applied as it is, the carry is caused by the influence of the AC component carry error. The amount may not be corrected correctly. For example, even when a transport operation of a 1/4 inch transport amount is performed between pass 1 and pass 2 as in the case of printing a measurement pattern, the rotation position of the transport roller 23 at the start of transport is If the measurement pattern is different from the printing time, even if the target carry amount is corrected with the correction value C (1), the carry amount is not correctly corrected. If the rotation position of the conveyance roller 23 at the start of conveyance is 180 degrees different from that at the time of printing the measurement pattern, the conveyance amount is not corrected correctly because of the influence of the AC component conveyance error. Can get worse.

Therefore, in the reference example, in order to correct only the DC component transport error, a correction amount for correcting the DC component transport error by averaging four correction values C as shown in the following equation. Ca is calculated.
Ca (i) = {C (i-1) + C (i) + C (i + 1) + C (i + 2)} / 4

Here, the reason why the correction value Ca for correcting the DC component transport error can be calculated by the above equation will be described.
As described above, the correction value C (i) of the transport operation performed between the pass i and the pass i + 1 is “6.35 mm” (1/4 inch, that is, the theoretical distance between the line Li and the line Li + 1. ) Minus “R (i + 1) −R (i)” (the absolute position of the line Li + 1 and the actual distance between the lines Li). Then, the above equation for calculating the correction value Ca has the following meaning.
Ca (i) = [25.4 mm- {R (i + 3) -R (i-1)}] / 4

That is, the correction value Ca (i) is a difference between the distance between two lines (line Li + 3 and line Li-1) that should theoretically be 1 inch apart and 1 inch (the conveyance amount for one rotation of the conveyance roller 23). The value divided by. In other words, the correction value Ca (i) is a value corresponding to the interval between the line Li-1 and the line Li + 3 formed after the line is formed and conveyed for 1 inch.
Therefore, the correction value Ca (i) calculated by averaging the four correction values C is not affected by the AC component transport error and is a value reflecting the DC component transport error.

  The correction value Ca (2) of the transport operation performed between pass 2 and pass 3 is a value obtained by dividing the sum of correction values C (1) to C (4) by 4 (correction value C (1)). (Average value of .about.C (4)). In other words, the correction value Ca (2) is a value corresponding to the interval between the line L1 formed in the pass 1 and the line L5 formed in the pass 5 after the line L1 is formed and conveyed for 1 inch. Become.

  Further, when i-1 is equal to or less than zero when calculating the correction value Ca (i), C (1) is applied as the correction value C (i-1). For example, the correction value Ca (1) of the transport operation performed between pass 1 and pass 2 is calculated as {C (1) + C (1) + C (2) + C (3)} / 4. Further, when i + 1 is 20 or more when calculating the correction value Ca (i), C (19) is applied to C (i + 1) for calculating the correction value Ca. Similarly, when i + 2 is 20 or more, C (i + 2) applies C (19). For example, the correction amount Ca (19) of the conveyance operation performed between the pass 19 and the pass 20 is calculated as {C (18) + C (19) + C (19) + C (19)} / 4.

  In this way, the computer 110 calculates the correction values Ca (1) to Ca (19). Thus, a correction value for correcting the DC component transport error is obtained for each 1/4 inch range.

=== Storage of Correction Value (S104) ===
Next, the computer 110 stores the correction value in the memory 63 of the printer 1 (S104).
FIG. 22 is an explanatory diagram of a table stored in the memory 63. The correction values stored in the memory 63 are the correction values Ca (1) to Ca (19) in the NIP state and the correction value Cb in the non-NIP state. Further, boundary position information for indicating a range to which each correction value is applied is also stored in the memory 63 in association with each correction value.

  The boundary position information associated with the correction value Ca (i) is information indicating the position (theoretical position) corresponding to the line Li + 1 of the measurement pattern, and the correction value Ca (i) is applied to this boundary position information. The boundary of the lower end side of the range to be shown is shown. Note that the upper end side boundary can be obtained from the boundary position information associated with the correction value Ca (i−1). Therefore, for example, the application range of the correction value C (2) is a range between the position of the line L1 and the position of the line L2 (where the nozzle # 90 is located) with respect to the paper S. Note that since the range in which the non-NIP state is set is known, the boundary value information may not be associated with the correction value Cb.

  In the printer manufacturing factory, a table reflecting individual characteristics of each printer is stored in the memory 63 for each printer manufactured. The printer storing this table is packed and shipped.

=== Conveying operation during printing under the user ===
When printing is performed under the user who purchased the printer, the controller 60 reads the table from the memory 63, corrects the target transport amount based on the correction value, and performs the transport operation based on the corrected target transport amount. Do. Hereinafter, the state of the conveyance operation at the time of printing under the user will be described.

  FIG. 23A is an explanatory diagram of correction values in the first case. In the first case, the position of the nozzle # 90 before the transport operation (relative position with respect to the paper) matches the boundary position on the upper end side of the application range of the correction value Ca (i), and the position of the nozzle # 90 after the transport operation Corresponds to the boundary position on the lower end side of the application range of the correction value Ca (i). In such a case, the controller 60 sets the correction value Ca (i), drives the carry motor 22 with the target value obtained by adding the correction value Ca (i) from the initial target carry amount F, and carries the paper. To do.

  FIG. 23B is an explanatory diagram of correction values in the second case. In the second case, the position of the nozzle # 90 before and after the transport operation is both within the application range of the correction value Ca (i). In such a case, the controller 60 sets a value obtained by multiplying the ratio F / L between the initial target transport amount F and the transport range length L of the applicable range by Ca (i) as a correction value. Then, the controller 60 drives the carry motor 22 with the target value obtained by adding the correction value Ca (i) × (F / L) from the initial target carry amount F to carry the paper.

  FIG. 23C is an explanatory diagram of correction values in the third case. In the third case, the position of the nozzle # 90 before the transport operation is within the application range of the correction value Ca (i), and the position of the nozzle # 90 after the transport operation is within the application range of the correction value Ca (i + 1). is there. Here, of the target transport amount F, the transport amount within the application range of the correction value Ca (i) is F1, and the transport amount within the application range of the correction value Ca (i + 1) is F2. In such a case, the controller 60 sets the sum of a value obtained by multiplying Ca (i) by F1 / L and a value obtained by multiplying Ca (i + 1) by F2 / L as a correction value. Then, the controller 60 drives the carry motor 22 with the target value obtained by adding the correction value from the initial target carry amount F to carry the paper.

  FIG. 23D is an explanatory diagram of correction values in the fourth case. In the fourth case, the paper is conveyed so as to pass through the application range of the correction value Ca (i + 1). In such a case, the controller 60 sets the sum of a value obtained by multiplying Ca (i) by F1 / L, a value obtained by multiplying Ca (i + 1) and Ca (i + 2) by F2 / L as a correction value. Then, the controller 60 drives the carry motor 22 with the target value obtained by adding the correction value from the initial target carry amount F to carry the paper.

  Thus, when the controller corrects the initial target transport amount F and controls the transport unit based on the corrected target transport amount, the actual transport amount is corrected to become the initial target transport amount F, The DC component transport error is corrected.

  By the way, if the correction value is calculated as described above, when the target carry amount F is small, the correction value is also small. If the target transport amount F is small, it is considered that the transport error that occurs when the transport is performed is small. Therefore, if the correction value is calculated as described above, a correction value that matches the transport error that occurs during transport can be calculated. In addition, since the applicable range is set every ¼ inch for each correction value Ca, the DC component transport error that changes in accordance with the relative position between the paper S and the head 41 can be corrected accurately. can do.

=== Correction of transport amount when paper sizes are different ===
In the carry amount correction of the above-described reference example, a correction value table is stored, and the carry amount is corrected when the paper is carried using these correction values. However, it is impossible to correct the carry amount as described above for a sheet having a size for which no correction value table is stored. At this time, even when a sheet having a size for which no correction value table is stored is conveyed, accurate conveyance can be performed if the above-described conveyance amount correction can be performed.

  In the method described below, a predetermined correction value in the correction value table is not used, or the predetermined correction value is used a plurality of times, and a sheet having a size for which the correction value table is not stored is conveyed. Even in this case, it is possible to cope with the conveyance amount correction.

<When transporting smaller size paper>
First, a case where printing is performed on a sheet smaller than the sheet size for which the correction value table is stored in the memory 63 will be described. At this time, the memory 63 stores a table of correction values corresponding to a size of 101.6 mm × 152.4 mm (4 inches × 6 inches: hereinafter referred to as “4 × 6 sizes”). To do. A case will be described in which a sheet of 89 mm × 127 mm (hereinafter referred to as “L size”), which is a size for which no correction value table is stored, is conveyed.

  FIG. 24 is an explanatory diagram of a corresponding range of the correction value C (i) applied to 4 × 6 size paper. Here, when the test sheet TS is conveyed ideally, the line interval is set to 1/8 inch. The reason why the line interval is narrowed in this way is to ensure higher conveyance accuracy than in the above-described reference example.

  In the above-described reference example, there is no conveyance error, and the line interval when the sheet is conveyed ideally becomes 1/4 inch. Therefore, here, the number is larger than the number of lines described above. Here, the lines are used from L1 to L39. Correspondingly, correction values C (1) to C (38) are prepared. The correction value C at this time is obtained by the same method as in the reference example.

The correction value Ca for correcting the DC component transport error is calculated by averaging eight correction values C as shown in the following equation.
Ca (i) = {C (i-3) + C (i-2) + C (i-1)
+ C (i) + C (i + 1) + C (i + 2)
+ C (i + 3) + C (i + 4)} / 8

  In this case, too, when i-3, i-2, i-1 are equal to or less than zero when calculating the correction value Ca (i), the correction values C (i-3) to C (i-1) are calculated. Applies C (1). When calculating the correction value Ca (i), if i + 1 is equal to or greater than 38, C (38) is applied to C (i + 1) to C (i + 4) for calculating the correction value Ca.

  In this way, the correction value Ca (1) to the correction value Ca (38) are calculated. As a result, a correction value for correcting the DC component transport error is obtained for each 1/8 inch range.

  FIG. 25 is an explanatory diagram of a table (4 × 6 sizes) stored in the memory 63. The boundary position information associated with the correction value Ca (i) is information indicating the position (theoretical position) corresponding to the line Li + 1 of the measurement pattern, and the correction value Ca (i) is applied to this boundary position information. The boundary of the lower end side of the range to be shown is shown. Here, correction values Ca (1) to Ca (38) exist. Here, printing is performed on L-size paper having a size smaller than 4 × 6 size while correcting the conveyance error based on the correction value Ca.

  Incidentally, as described above, the sheet is conveyed by the conveyance roller 23 and the paper discharge roller 25. Naturally, it is considered that when the sheet is conveyed by only one of the rollers, the variation in the conveyance error is large, and when the sheet is conveyed by both rollers, the variation in the conveyance error is small.

  Here, the boundary position corresponding to the relative position between the head and the sheet when the sheet S is conveyed by both the conveyance roller and the discharge roller is defined as the boundary position of the normal region. On the other hand, the boundary position corresponding to the relative position between the head and the sheet when the sheet is conveyed by either the conveyance roller or the sheet discharge roller is set as the boundary position of the non-normal area. In other words, the non-normal area is an area having a width between the conveyance roller and the paper discharge roller in the printer 1 from each end in the sheet conveyance direction. A region other than the non-normal region is a normal region.

  Among the boundary positions of the normal area, there is a boundary position of the stable area corresponding to a portion with less variation in the transport error. The boundary position of the stable region is the position of the head when the paper S is transported by the transport roller and the paper discharge roller, and the predetermined region of the paper S is fed while being bent by the paper feed tray (paper feed tray). This is the boundary position corresponding to the relative position to the paper. Specifically, the boundary position corresponds to the relative position when the rear portion of the sheet is fed in contact with the sheet feed tray. This is considered that when the paper S enters the transport roller while being bent by the paper feed table, the force that enters the transport roller of the paper is constant, and therefore it is considered that the fluctuation of the transport error is further reduced.

  FIG. 26A is a diagram illustrating the initial position of the sheet when the sheet is conveyed by the conveyance roller and the discharge roller. In the initial stage, the vicinity of the upper end of the sheet (near the downstream side of the sheet) is sandwiched between the transport roller and the discharge roller. Most of the trailing edge of the sheet is in contact with the sheet feeding table 29. FIG. 26B is a diagram illustrating the position of the sheet at the later stage when the sheet is conveyed by the conveyance roller and the discharge roller. In the latter stage, the portion in contact with the paper feed tray 29 near the rear end of the paper (near the upstream side of the paper) is reduced.

  Referring to FIG. 26A, there is a portion where the paper is bent between the paper feed table 29 and the transport roller (a portion surrounded by a dotted line in the drawing). The amount of deflection of the sheet is considered to have substantially the same amount of deflection from the initial stage to the later stage of sheet conveyance. On the other hand, referring to FIG. 26B, in the latter stage, most of the upstream sheet is not in contact with the sheet feed table 29, and the amount of deflection at the portion surrounded by the dotted line in the figure increases as the sheet is conveyed. It will change.

  The change in the amount of deflection of the sheet affects the change in the conveyance error. Therefore, in the initial stage of transporting a sheet with a small change in the amount of deflection of the sheet, although a transport error occurs, the amount of change in the transport error is small. The relative position of the sheet at the initial stage where the amount of deflection of the sheet is small is when the downstream portion of the sheet is in the vicinity of the head. Therefore, it is considered that the variation amount of the conveyance error when the downstream portion of the sheet is in the vicinity of the head is smaller than the variation amount of the conveyance error when the upstream portion of the sheet is in the vicinity of the head.

  By the way, when the paper size is reduced, it can be considered that the portion where the change in the amount of deflection is small is reduced. Taking these into consideration, a graph of the estimated transport error when the paper size is reduced by removing the transport error of the portion where the change in the deflection amount is small is removed from the graph of the transport error of the larger size paper. It is thought that it can be obtained.

  Since the correction value is a value that cancels the conveyance error, it can be considered that the value of the conveyance error is reversed. Therefore, when creating a correction value table for a smaller paper size from a correction value table for a predetermined size paper, the correction value corresponding to the portion where the change in the deflection amount is small is deleted. Can be created. In this case, since it is desirable to delete the correction value corresponding to the portion where the variation in the transport error is as small as possible, when the downstream portion of the sheet is in the vicinity of the head, the correction value should be deleted sequentially from the corresponding one. Is desirable.

  On the other hand, when creating a correction value table of a larger size from a table of paper of a predetermined size, the correction value of the portion where the change in the deflection amount is small is used a plurality of times, and the insufficient correction value is interpolated. You can make it like that. This is because when the size of the paper to be conveyed is increased, it is considered that the portion where the change in the deflection amount is small increases.

  The boundary position of the stable region is determined in advance according to the paper size. Here, L12 to L19 are determined as the boundary position Li of the stable area of the 4 × 6 sheet. The correction values associated with the boundary position information indicating the position (theoretical position) corresponding to the line L at this time are Ca (11) to Ca (18). Therefore, when creating a correction value table for a smaller sheet based on a 4 × 6 size correction value table, the correction value in this stable region is deleted, and a correction value table for a small sheet is created. Is done.

  FIG. 27 is an L size table created based on a 4 × 6 size table. The newly created L-size correction value table is obtained by deleting Ca (11) to Ca (18) out of 4 × 6 size correction values Ca (1) to Ca (38). It has become. Therefore, the correction values of Ca (19) to Ca (38) correspond to the theoretical position corresponding to L31 from the theoretical position corresponding to L12, as much as these correction values are deleted.

  Of the correction values corresponding to when the paper is being transported to both the transport roller 23 and the paper discharge roller 25, the correction value corresponding to the relative position when the downstream portion of the paper is below the head is: Ca (11) to C (19) (C (19) is a correction value corresponding to the relative position when the center of the sheet is at the lower part of the head). Ca (11) to Ca (18) are corrections corresponding to seven consecutive relative positions among the correction values associated with the relative positions when the downstream portion of the sheet S is located below the head. Value.

  In this way, since a correction value table for a small size paper can be created based on a correction value table for a predetermined size paper, printing of a paper size for which no table is stored in the memory is possible. Even when performing the above, it is possible to transport the paper while correcting the transport error.

<When transporting larger size paper>
Here, a case will be described in which printing is performed on a sheet having a larger sheet conveyance direction than the sheet size stored in the memory 63 as a correction value table. At this time, it is assumed that a correction value corresponding to a size of 101.6 mm × 152.4 mm (4 × 6 sizes) is stored in the memory 63. A case will be described in which printing is performed on a sheet of 102 mm × 181 mm (hereinafter referred to as “high-definition format”) that is a size in which no correction value is stored.

  Again, a correction value table corresponding to the size of another sheet is created from the 4 × 6 size correction value table. Also here, as shown in FIG. 24, when the test sheet TS is conveyed ideally, the line interval is set to 1/8 inch. The memory 63 stores a table (4 × 6 sizes) as shown in FIG. Further, the above-mentioned non-normal area and the range of the normal area are the same as those in the case of “conveying a smaller size sheet”. The range of the stable region is relative, and here, L12 to L18 are determined as the boundary position Li of the stable region.

  Here, when creating a correction value table for a larger-sized sheet based on a 4 × 6 size correction value table, the correction values for the stable region are interpolated to the correction values that are insufficient. Thus, a correction value table is created. Further, which correction value among the correction values corresponding to the stable region is preferentially used for the interpolation is arbitrarily determined in advance. This is because, since there is little variation in the transport error in the stable region, it is considered that almost the same value is obtained regardless of which correction value corresponding to the stable region is used. Here, it is determined that the correction value Ca (14) is used for interpolation. Therefore, seven correction values Ca (14) are interpolated in the rear end direction from the position of L15 corresponding to Ca (14).

  FIG. 28 is a high-definition correction value table created based on a 4 × 6 size table. The newly created high-definition correction values here are such that seven Ca (14) are interpolated, and therefore eight correction values Ca (14) continue.

  In this way, since a correction value table for a large size paper can be created based on a correction value table for a predetermined size paper, the correction value table is not stored in the memory 63. Even when printing paper, the paper can be transported while correcting the transport error.

By the way, in the conveyance amount correction of the above-described reference example, a correction value table is stored and the conveyance amount is corrected at the time of paper conveyance using these correction values. The carry amount cannot be corrected using this correction value. This is because different types of paper have different transport errors and correspondingly different correction values.
Therefore, even when a sheet of a type for which no correction value table is stored is conveyed, if there is a method capable of correcting the conveyance amount as in the reference example, accurate conveyance can be performed.

  In the following method, a description will be given of a case where a sheet of a type different from the sheet corresponding to the correction value table stored in the memory 63 is conveyed.

<Correction amount correction for different types of paper>
FIG. 29 is a graph showing transport errors for 4 × 6 paper type A, paper type B, and paper type C. When the transport errors of these paper types A to C are compared, it can be seen that the shapes of the graphs are similar. Then, it can be read that the shape is a parallel translation depending on the paper type. This is presumably because the amount of slip between the roller and the paper changes due to the different types of paper, and the transport error changes over the entire surface of the paper.

  As described above, since the transport error is totally translated in the positive or negative direction, when the paper type is changed, the transport amount correction value Ca is also generally determined. It is thought that the value will be translated.

  That is, when transporting a sheet different from the sheet type corresponding to the correction value table stored in the memory 63, the correction value is corrected by a predetermined amount and used. Also, the conveyance amount can be corrected.

For example, it is assumed that a table of correction values Ca for 4 × 6 sheet type A is stored in the memory 63. On the other hand, it is assumed that the correction value Ca ′ table for the 4 × 6 paper type B is not stored in the memory 63. At this time, if the correction amount of the correction amount from the paper type A to the paper type B is OFFSET, the correction amount Ca ′ of the paper type B is
Ca ′ (i) = OFFSET + Ca (i)
Can be obtained.

  As described above, by storing the correction amount in the memory 63 in advance, even when the conveyance is performed for a paper type that is not stored in the memory 63, the conveyance can be performed while correcting the target conveyance amount. Can be carried out with high accuracy.

  By the way, if the conveyance amount is corrected by the above-described method, it is necessary to obtain the correction amount in advance. In the embodiment described below, the correction amount used in the above-described method is obtained based on the conveyance error.

=== Embodiment ===
As described above, when a paper type different from the predetermined type stored in the memory 63 is conveyed, it is necessary to obtain a correction amount in advance. This correction amount needs to be stored in advance in a nonvolatile memory in the memory 63. In the following, how the correction amount is obtained will be described. The method described below is a method used to obtain a correction amount to be set in the printer 1 that transports paper mainly before shipment from the factory.

  FIG. 30 is a flowchart for explaining a method of obtaining the correction amount. This operation is performed in the correction amount calculation apparatus. The correction amount calculation device is realized by executing a program that performs the following operations on a computer.

  The correction amount calculation apparatus obtains a transport error for the 4 × 6 size (101.6 mm × 152.5 mm) paper type A (S321). The conveyance error is obtained by the same method as described above. The transport error is stored in a memory in the correction amount calculation device. Further, the correction amount calculation apparatus obtains a correction value Ca for correcting the target carry amount for the 4 × 6 sheet type A (S321). The correction value Ca is obtained by the same method as described above. The correction value Ca is stored in the memory of the correction amount calculation device. Here, the transport error and the correction value Ca are determined by the correction amount calculation device. However, the transport error and the correction value Ca that are determined in advance may be stored in the memory of the correction amount calculation device.

  The correction amount calculation apparatus obtains a conveyance error for the 4 × 6 sheet type B (S322). The conveyance error is obtained by the same method as described above. The transport error is stored in the memory of the correction amount calculation device. The transport error is determined by the correction amount calculation device, but the transport error determined in advance may be stored in the memory of the correction amount calculation device.

  Next, a correction amount for obtaining the correction value Ca 'for the paper type B is obtained (S323). As a method for obtaining the correction amount, a difference between the average value of the correction values of the paper type B and the average value of the correction values of the paper type A is obtained. The correction value is a difference in conveyance error between adjacent relative positions.

If the transport error of paper type A is e (i) and the correction value is Ca (i),
Ca (i) = e (i + 1) −e (i)
If the average value of correction values for paper type A is AVEca,
AVEca = {Ca (1) +... + Ca (n-1)} / (n-1)
= {E (n) -e (1)} / (n-1)
Similarly, when the conveyance error of paper type B is e ′ (i), the correction value is Ca ′ (i), and the average value of the correction values is AVEca ′,
AVEca ′ = {Ca ′ (1) +... + Ca ′ (n−1)} / (n−1)
= {E '(n) -e' (1)} / (n-1)
Since the correction amount OFFSET is the difference between the average value AVEca ′ of the correction value for paper type B and the average value AVEca of the correction value for paper type A,
OFFSET = AVEca'-AVEca
= {E '(n) -e' (1)} / (n-1)
-{E (n) -e (1)} / (n-1)
Is required.

  The obtained correction amount is stored in a non-volatile memory in the memory 63 before the printer 1 is shipped from the factory, and is used when transporting a paper type different from the paper type in which the correction value is stored. Become.

  In this way, the correction amount required when the correction value of a sheet of a material different from that of the sheet storing the correction value is obtained using the correction value of another sheet storing the correction value. Can be sought.

<Identification of unused correction values>
As described above, it is possible to carry a sheet while correcting the carry amount for a sheet smaller than a sheet having a predetermined size stored in the memory 63. At this time, it is necessary to obtain in advance which correction value among the correction values of the predetermined size paper is not used. Then, which correction value is not used (in other words, which correction value is used) needs to be stored in advance in the nonvolatile memory in the memory 63. In the following, how to determine a correction value that is not used among correction values of a predetermined size of paper will be described. The method described below is a method for setting which correction value is not used for the printer 1 that transports paper mainly before shipment from the factory.

  When deleting some correction values from the correction value table as correction values that are not used, it is desirable to delete the correction values corresponding to the portion where the variation in the transport error is small. This is because, as described above, when the paper size is reduced, it can be considered that the portion where the change in the deflection amount is small is reduced. This is because a portion where the change in the deflection amount is small corresponds to a portion where the variation in the transport error is small.

  FIG. 31 is a flowchart for explaining a method of determining a correction value that is not used. This operation is performed in the correction value determination device. The correction value determination device is realized by executing a program that causes the computer to perform the following operations.

  In the memory of the correction value determination device, a transport error for a 4 × 6 size (101.6 mm × 152.4 mm) sheet is stored in advance. The memory of the correction value determination device also stores a table of correction values Ca for 4 × 6 paper. This correction value table is obtained in advance by the method of the reference example described above.

  The computer prompts the user to enter a size for a smaller paper size that is different from the 4 × 6 size. Then, the user inputs a smaller paper size different from the 4 × 6 size (S291). Here, the description will be made assuming that an L size (89 mm × 127 mm) is input by the user.

  Next, the number of correction values that should not be used is obtained from the relationship between the sheet size for which the correction value table is stored in the memory and the sheet size input by the user (S292). Here, a 4 × 6 size correction value table is stored in advance, and the L size is input by the user. The number of correction values that should not be used is determined in advance based on the difference in size in the conveyance direction between the 4 × 6 size and the L size. In this case, the number of correction values that are not used is calculated as seven.

  Although the correction values that are not used are determined in advance because of the relationship between the two paper sizes, the number of correction values that are not necessary may be calculated from the sizes of these papers. For example, the difference in length in the transport direction between the two may be obtained, and the number of correction values that are not necessary for a short amount of small paper may be obtained from the relationship between the difference and the boundary position interval.

  Next, it is determined which correction value is not used among the correction values corresponding to the case where the central portion of the sheet passes under the head (S293). Here, the correction value corresponding to the portion with the smallest fluctuation amount of the transport error is not used.

  FIG. 32 is a graph showing a 4 × 6 size conveyance error obtained by actual measurement. The vertical axis of this graph indicates the transport error. The number on the horizontal axis of the graph indicates the correction value number i corresponding to the correction value Ca (i). The degree of change in the transport error in the graph is hereinafter referred to as a transport error fluctuation amount. The amount of change in the transport error appears as the degree of change in the slope of the diagram in the figure. Therefore, the amount of fluctuation is large at a location where the change in the slope of the diagram is large. For example, since the difference between the slope of the line between i = 36 and i = 37 and the slope of the line between i = 37 and i = 38 is large, the amount of fluctuation is large at i = 36 to 38. On the other hand, the difference between the slope of the line between i = 12 and i = 13 corresponding to the slightly downstream side from the center of the sheet and the slope of the line between i = 13 and i = 14 is small. = 12-14, the fluctuation amount is small. In general, it can be seen that the transport error has a large fluctuation amount at the edge of the sheet and a small fluctuation amount in the portion corresponding to the above-described stable region.

As described above, the fluctuation amount of the conveyance error can be obtained by obtaining the degree of change in the slope of the diagram. The slope of the diagram is the difference between adjacent transport errors. Therefore, the fluctuation amount of the conveyance error is obtained by adding the square of the difference between the difference between the adjacent conveyance errors (the inclination of the conveyance error) and the difference between the adjacent conveyance errors. If the variation amount of the conveyance error is V (i) and the conveyance error is e (i),

  Here, e 'is the slope of the transport error e. The value of N is the same as the number of correction values that are not used. Here, the value of N is 8. This is because it is necessary to delete eight correction values when creating a correction value table for L size from a 4 × 6 size correction value table.

  In (Expression 1), N (here, 8) squares of differences between adjacent slopes are added. Therefore, the fluctuation amount V has a property of increasing when the N sums of squares of differences between adjacent slopes are large. For this reason, when the difference between adjacent inclinations is large, the fluctuation amount V is large, and when the difference between adjacent inclinations is small, the fluctuation amount V is small. Even if the inclination of the diagram is large, the value of the fluctuation amount V is small if the adjacent inclinations are the same. On the other hand, even when the slope of the diagram itself is small, when the positive slope and the negative slope are repeated, the difference between the adjacent slopes is large, and as a result, the variation amount V becomes large.

  V (1) to V (29) are obtained from (Equation 1). Then, the computer obtains the smallest fluctuation amount V (i) among V (1) to V (29). Then, it is determined that the correction values Ca (i) to Ca (i + 7) corresponding to i to (i + 7) (eight) at the time of the smallest fluctuation amount V (i) are not used at the time of L size printing. This information is stored in the memory of the correction value determination device. The stored information is stored in the memory 63 of the printer 1 in the printer manufacturing process.

  The reason why the corresponding correction value is not used when the fluctuation amount V is the minimum is as follows. As described above, when a paper smaller than the paper whose correction value table is stored in the memory is conveyed, it is desirable to delete the correction value corresponding to the portion where the change in the deflection amount of the paper (FIG. 26) is small. In the portion where the change in the amount of deflection of the sheet is small, the variation in the transport error is also small. For this reason, the correction value corresponding to the portion with the smallest variation in the transport error is not used here.

  In the above reference example, the correction values Ca (11) to Ca (18) are not used. This is because the minimum fluctuation amount among the fluctuation amounts obtained in (Equation 1) is V (11). Referring again to FIG. 32, it can be seen that the slope of the conveyance error changes substantially constant when the value of i is between 11 and 18. This indicates that the difference between adjacent transport errors is the most constant in this range.

Here, as shown in (Equation 1), as the variation amount, the difference between adjacent transport errors and the difference between adjacent transport errors are added to the square value of the difference. It is good also as calculating | requiring a fluctuation amount by another type | formula. For example, the variation amount of the conveyance error may be obtained by using the following variance value σ ² .

As described above, the average value of the gradient of the transport error e used here is not the average value in the entire range of i = 1 to 38, but is continuous in the range of i to i + N−1 (N = 8 here). This is the average value of the slope of the transport error. This is because it is necessary to determine N consecutive correction values that are not used in the present embodiment, so that the average value of the slopes of the N consecutive transport errors e is obtained in order to obtain the variance value σ ^2. I used it.

  In this way, it is possible to determine not to use the correction value corresponding to the smallest amount of variation in the transport error. Therefore, when transporting a sheet having a different size from the sheet storing the correction value. In addition, it is possible to determine which correction value of the stored paper should be used for conveyance.

<Identification of correction value used for interpolation>
As described above, it is possible to carry the paper while correcting the carry amount for a paper larger than the paper of a predetermined size stored in the memory 63. At this time, it is necessary to obtain in advance which correction value among the correction values of the predetermined size paper is to be used a plurality of times. The correction value to be used a plurality of times needs to be stored in advance in the nonvolatile memory in the memory 63. Hereinafter, how to obtain a correction value to be used a plurality of times among correction values of a predetermined size of paper will be described. The method described below is also a method for setting which correction value is used a plurality of times for the printer 1 that transports paper mainly before shipment from the factory.

  As a predetermined correction value is used a plurality of times, when interpolation is performed for a correction value that is insufficient in the correction value table, a correction value corresponding to a portion with a small variation in transport error is used a plurality of times. desirable. This is because when the paper size is increased, it can be considered that the portion where the change in the deflection amount is small is enlarged. This is because the portion where the change in the deflection amount is small corresponds to the portion where the variation error of the transport error is small.

  FIG. 33 is a flowchart for explaining a method of determining a correction value to be used a plurality of times. This operation is also performed in the correction value determination device. The correction value determination device is realized by executing a program that causes the computer to perform the following operations.

  The memory of the correction value determining device stores in advance a 4 × 6 sheet conveyance error. The memory of the correction value determination device also stores a table of correction values Ca for 4 × 6 paper. This correction value table is obtained in advance by the method of the reference example described above.

  The computer prompts the user to enter a size for a larger paper size that is different from the 4 × 6 size. Then, the user inputs a larger paper size having a size different from the 4 × 6 size (S311). Here, the description will be made assuming that a high-definition size (102 mm × 181 mm) is input by the user.

  Next, the number of correction values to be used a plurality of times (the number of correction values to be interpolated) is determined based on the relationship between the sheet size for which the correction value table is stored in the memory in advance and the sheet size input by the user. ) Is obtained (S312). Here, a 4 × 6 size correction value table is stored in advance, and a high-definition size is input by the user. The number of correction values to be interpolated is determined in advance from the difference in size in the conveyance direction between the 4 × 6 size and the high vision size. In this case, the number of correction values to be interpolated is obtained as 7.

  The number of correction values to be interpolated is determined in advance because of the relationship between the sizes of the two sheets. However, it is also possible to calculate how many correction values should be interpolated from the sizes of these sheets. Good. For example, the difference between the lengths in the transport direction may be obtained, and the number of correction values that need to be replenished for a long large sheet may be obtained from the relationship between the difference and the boundary position interval.

Next, it is determined which correction value is used a plurality of times among correction values corresponding to the case where the central portion of the sheet passes under the head (S313). Here, one of the correction values corresponding to the portion with the smallest fluctuation amount of the transport error is used a plurality of times.
The fluctuation amount of the conveyance error can be obtained using (Equation 1).
In the above description, the value of N is set to 8 in order to delete the eight correction values. Here, since the number of correction values to be interpolated is 7, the amount of variation is obtained by setting the value of N to 7.

  V (1) to V (30) are obtained from (Equation 1). Then, the computer obtains the smallest fluctuation amount V (i) among V (1) to V (30). Then, one correction value among correction values C (i) to Ca (i + 6) corresponding to i to (i + 6) at the time of the smallest variation V (i) is used a plurality of times during high-definition printing. Decide to do. Here, among Ca (i) to Ca (i + 6), it is determined that the central Ca (i + 3) is used a plurality of times. Information on correction values used a plurality of times is stored in the memory of the correction value determination device. The stored information is stored in the memory 63 of the printer 1 in the printer manufacturing process.

  The reason why one of the corresponding correction values is used a plurality of times when the fluctuation amount V is the minimum is that the difference between the corresponding adjacent conveyance errors changes at the most constant value at this time. is there. When the difference in transport error changes at a constant value, the correction value for correcting the transport error is also constant. That is, here, a relative position corresponding to a place where the correction value becomes constant is found, and a certain correction value corresponding to this position is interpolated.

In the above-described reference example, the correction value Ca (14) is used a plurality of times. This is because the minimum fluctuation amount among the fluctuation amounts obtained by (Equation 1) is V (11). Here, it has been determined in advance that Ca (i + 3) among the correction values Ca (11) to Ca (18) is adopted, but this is the other of Ca (i) to Ca (i + 6). Any correction value may be used, and it may be selected at random.
Similarly to the above, the variation amount may be obtained as a variance value using (Equation 2).

  In this way, it is possible to obtain a correction value corresponding to the smallest variation in the conveyance error so that the correction value is used a plurality of times. Therefore, a sheet having a different size from the sheet storing the correction value is conveyed. In this case, it is possible to determine which correction value of the stored paper should be used for conveyance.

=== Other Embodiments ===
The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About the head>
In the above-described embodiment, ink is ejected using a piezoelectric element. However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.
In the above-described embodiment, the head is provided on the carriage. However, the head may be provided in an ink cartridge that is detachable from the carriage.

=== Summary ===
(1) The correction amount calculation method described above is a transport error with respect to a target transport amount when transporting a predetermined type of paper, and is associated with the relative position between the paper and the head for recording on the paper. A step of obtaining a plurality of conveyance errors. The correction amount calculation method includes a step of obtaining a plurality of transport errors corresponding to the target transport amount when transporting another type of paper different from the predetermined type and corresponding to the relative position. . Further, the correction amount calculation method is a correction amount for obtaining a correction value for correcting a target transport amount when transporting a predetermined type of paper, and is a correction value corresponding to a transport error of other types of paper. And a step of calculating a correction amount for obtaining a correction value corresponding to the transport error of the predetermined type of paper based on the transport error of the predetermined type of paper and the transport error of other types of paper. .
In this way, the correction amount required when the correction value of a sheet of a material different from that of the sheet storing the correction value is obtained using the correction value of another sheet storing the correction value. Can be sought.

(2) Further, the correction amount described above is the average value of the correction value of the paper type B obtained based on the conveyance error of the paper type B, and the paper type A obtained based on the conveyance error of the paper type A. It is the difference from the average value of the correction values.
In this way, the correction amount can be obtained based on the transport error of a predetermined type of paper (paper type A) and the transport error of another type of paper (paper type B).

(3) Further, it is assumed that the above-mentioned predetermined type of paper has a predetermined size. Then, based on the variation amount of the conveyance error of the paper having the predetermined size, the target conveyance amount at the time of conveying other size paper is corrected from the plurality of correction values of the paper having the predetermined size. It is desirable that the method further includes a step of determining a correction value.
By doing so, it is possible to determine which correction value of the stored paper should be used when transporting a paper having a different size from the paper storing the correction value. .

(4) Further, when the size in the transport direction of other sizes of paper is smaller than that of the predetermined size, the step of determining the correction value described above is relative to the case where the amount of change in transport error is small. It is desirable to include a step of determining a correction value for correcting a target transport amount when transporting other sizes of paper so as not to use continuous correction values corresponding to positions.
By doing so, it is determined which correction value of the stored paper should not be used when carrying a paper whose correction value is smaller than that of the stored paper so as to perform the transport amount correction. be able to.

(5) Further, when the size of the other size paper in the transport direction is larger than that of the predetermined size paper, the step of determining the correction value described above is relative to the case where the variation amount of the transport error is small. The method may include a step of determining a correction value for correcting a target transport amount when transporting another size of paper so that a part of the continuous correction value corresponding to the position is used a plurality of times.
In this way, when the paper whose correction value is larger than the stored paper is transported, which correction value of the stored paper should be used a plurality of times to carry out the transport amount correction. Can be decided.

(6) Moreover, the correction amount calculation apparatus in the embodiment includes a memory and an arithmetic device. The memory of the correction amount calculation device is a transport error with respect to the target transport amount when transporting a predetermined type of paper, and a plurality of transport errors associated with the relative positions of the paper and the head for recording on the paper Remember. In addition, this memory stores a plurality of transport errors associated with the relative positions, which are transport errors with respect to the target transport amount when transporting another type of paper different from the predetermined type.
The arithmetic unit of the correction amount calculation device is a correction amount for obtaining a correction value for correcting a target transport amount when transporting a predetermined type of paper, and a correction value corresponding to a transport error of other types of paper A correction amount for obtaining a correction value corresponding to the transport error of a predetermined type of paper by adding to the above is calculated based on the transport error of a predetermined type of paper and the transport error of the other types of paper.
In this way, the correction amount required when the correction value of a sheet of a material different from that of the sheet storing the correction value is obtained using the correction value of another sheet storing the correction value. Can be sought.

(7) Needless to say, there is a program for causing the correction amount calculation device to execute the correction amount calculation method described above.

1 is a block diagram of an overall configuration of a printer 1. FIG. FIG. 2A is a schematic diagram of the overall configuration of the printer 1. FIG. 2B is a cross-sectional view of the overall configuration of the printer 1. It is explanatory drawing which shows the arrangement | sequence of a nozzle. 4 is an explanatory diagram of a configuration of a transport unit 20. FIG. 6 is a graph for explaining AC component transport error. It is a graph (conceptual figure) of the conveyance error which arises when conveying paper. It is a flowchart until it determines the correction value for correct | amending conveyance amount. FIG. 8A to FIG. 8C are explanatory diagrams of how the correction value is determined. It is explanatory drawing of the mode of printing of the pattern for a measurement. FIG. 10A is a longitudinal sectional view of the scanner 150. FIG. 10B is a top view of the scanner 150 with the upper lid 151 removed. It is a graph of the error of the reading position of a scanner. FIG. 12A is an explanatory diagram of the reference sheet SS. FIG. 12B is an explanatory diagram showing a state in which the test sheet TS and the reference sheet SS are set on the platen glass 152. It is a flowchart of the correction value calculation process in S103. It is explanatory drawing of a division | segmentation (S131) of an image. FIG. 15A is an explanatory diagram illustrating a state where the inclination of the image of the measurement pattern is detected. FIG. 15B is a graph of the gradation values of the extracted pixels. It is explanatory drawing of the mode of the detection of the inclination at the time of printing of the pattern for a measurement. It is explanatory drawing of the margin amount X. FIG. FIG. 18A is an explanatory diagram of an image range used when calculating the position of a line. FIG. 18B is an explanatory diagram of calculation of the position of the line. It is explanatory drawing of the position of the calculated line. It is explanatory drawing of calculation of the absolute position of the i-th line of the pattern for a measurement. It is explanatory drawing of the range to which correction value C (i) respond | corresponds. It is explanatory drawing of the table memorize | stored in the memory. It is explanatory drawing of the correction value in a 1st case. It is explanatory drawing of the correction value in a 2nd case. It is explanatory drawing of the correction value in a 3rd case. It is explanatory drawing of the correction value in a 4th case. It is explanatory drawing of the range which the correction value C (i) applied to 4x6 size paper respond | corresponds. It is explanatory drawing of the table (4x6 size) memorize | stored in the memory 63. FIG. FIG. 26A is a diagram illustrating the initial position of the sheet when the sheet is conveyed by the conveyance roller and the discharge roller, and FIG. 26B is a case where the sheet is conveyed to the conveyance roller and the discharge roller. FIG. 6 is a diagram showing the position of the paper in the later stage in FIG. This is an L size table created based on a 4 × 6 size table. It is a table of high-vision format correction values created based on a 4 × 6 format table. 4 is a graph showing transport errors for 4 × 6 paper type A, paper type B, and paper type C. FIG. It is a flowchart for demonstrating the method of calculating | requiring correction amount. It is a flowchart for demonstrating the method of determining the correction value which is not used. It is a graph which shows the conveyance error of 4x6 size actually measured and calculated | required. It is a flowchart for demonstrating the method of determining the correction value used in multiple times.

Explanation of symbols

1 printer, 110 computer,
20 transport unit, 21 paper feed roller, 22 transport motor, 23 transport roller,
24 platen, 25 paper discharge roller, 26 driven roller, 27 driven roller,
30 Carriage unit, 31 Carriage, 32 Carriage motor,
40 head units, 41 heads,
50 detector groups, 51 linear encoders,
52 Rotary encoder, 521 scale, 522 detector,
53 Paper detection sensor, 54 Optical sensor,
60 controller, 61 interface unit, 62 CPU,
63 memory, 64 unit control circuit,
150 scanner, 151 top cover, 152 platen glass,
153 reading carriage, 154 guide section, 155 moving mechanism,
157 exposure lamp, 158 line sensor, 159 optical system,
TS test sheet, SS reference sheet

Claims (7)

Obtaining a plurality of transport errors corresponding to the target transport amount when transporting a predetermined type of medium and corresponding to the relative positions of the medium and a head for recording on the medium;
A plurality of transport errors corresponding to a target transport amount when transporting another type of medium different from the predetermined type, and a plurality of transport errors associated with the relative position;
A correction amount for obtaining a correction value for correcting a target transport amount when transporting the predetermined type of medium, which is added to a correction value corresponding to a transport error of the other type of medium and the predetermined amount Calculating a correction amount for obtaining a correction value corresponding to a transport error of a type of medium based on the transport error of the predetermined type of medium and the transport error of the other type of medium;
Correction amount calculation method including   The correction amount is determined based on an average value of correction values of the predetermined type of medium determined based on the transport error of the predetermined type of medium and the transport error of the other type of medium. The correction amount calculation method according to claim 1, wherein the correction amount calculation method is a difference from an average value of correction values of other types of media. The medium has a predetermined size;
In order to correct a target transport amount when transporting a medium of another size from a plurality of correction values of the medium having the predetermined size, based on a variation amount of a transport error of the medium having the predetermined size. The correction amount calculation method according to claim 1, further comprising a step of determining a correction value.   The step of determining the correction value corresponds to the relative position when the variation amount of the conveyance error is small when the size of the other size medium in the conveyance direction is smaller than the medium of the predetermined size. The correction amount calculation method according to claim 3, further comprising a step of determining a correction value for correcting a target transport amount when transporting the medium having the other size so that a continuous correction value is not used.   The step of determining the correction value corresponds to the relative position when the variation amount of the transport error is small when the transport direction size of the other size medium is larger than the predetermined size medium. 4. The method according to claim 3, further comprising: determining a correction value for correcting a target transport amount when transporting the medium having the other size so that a part of the continuous correction value is used a plurality of times. Correction amount calculation method. Memory,
A plurality of transport errors corresponding to the relative positions of the medium and a head for recording on the medium, which are transport errors with respect to a target transport amount when transporting a predetermined type of medium;
A memory for storing a plurality of transport errors corresponding to a target transport amount when transporting another type of medium different from the predetermined type, and a transport error associated with the relative position;
An arithmetic unit,
A correction amount for obtaining a correction value for correcting a target transport amount when transporting the predetermined type of medium, which is added to a correction value corresponding to a transport error of the other type of medium and the predetermined amount An arithmetic unit that calculates a correction amount for obtaining a correction value corresponding to a transport error of a type of medium based on the transport error of the predetermined type of medium and the transport error of the other type of medium;
A correction amount calculation device comprising: A program for operating the correction amount calculation device,
Obtaining a plurality of transport errors corresponding to the target transport amount when transporting a predetermined type of medium and corresponding to the relative positions of the medium and a head for recording on the medium;
A plurality of transport errors corresponding to a target transport amount when transporting another type of medium different from the predetermined type, and a plurality of transport errors associated with the relative position;
A correction amount for obtaining a correction value for correcting a target transport amount when transporting the predetermined type of medium, which is added to a correction value corresponding to a transport error of the other type of medium and the predetermined amount Calculating a correction amount for obtaining a correction value corresponding to a transport error of a type of medium based on the transport error of the predetermined type of medium and the transport error of the other type of medium;
A program for causing the correction amount calculation apparatus to execute

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