JP2008028737A - Method of calculating print position of pattern on medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To calculate the print position of a pattern, printed on a medium, on the medium with high precision by using a scanner. <P>SOLUTION: The method of calculating the print position of the pattern on the medium is characterized including: a first read step of reading a scale having graduations in a prescribed direction by the scanner to generate image data of the scale; a second read step of reading the medium where the pattern is printed by the scanner to generate image data of the medium; and a print position calculation step of calculating the print position of the pattern on the medium in the prescribed direction based upon the image data of the scale and the image data of the medium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for calculating a printing position of a pattern on a medium.

  2. Description of the Related Art An ink jet printer is known as a printing apparatus that transports a medium such as paper in the transport direction and performs printing on the medium with a head. In such a printing apparatus, if a transport error occurs when transporting the medium, the head cannot be printed 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, in Patent Document 1, a pattern is printed, the pattern is read by a reading unit, a correction value is calculated based on the reading result, and the conveyance amount is corrected based on the correction value when an image is recorded. Proposed.
JP-A-5-96796

Here, a so-called scanner can be used as the reading unit. In this case, the pattern is read by the scanner to generate image data of the pattern, the print position of the pattern is detected based on the image data, and the correction value is calculated based on the detected position. Become.
However, the printing position of the pattern detected based on the image data includes a detection error of the scanner itself, such as an error of the reading position when the scanner reads the pattern, and thus the printing of the pattern on the medium is performed. It is difficult to determine the position with high accuracy.

  The present invention has been made in view of the above problems, and an object of the present invention is to print a pattern on a medium in which a print position on the medium of a pattern printed on the medium can be calculated with high accuracy using a scanner. The object is to provide a position calculation method.

The main invention for achieving the above object is:
A first reading step in which a scale calibrated in a predetermined direction is read by a scanner to generate image data of the scale;
A second reading step of reading a medium on which a pattern is printed by the scanner to generate image data of the medium;
A print position calculating step for calculating a print position for the predetermined direction of the pattern on the medium based on the image data of the scale and the image data of the medium;
A method for calculating a printing position of a pattern on a medium.

  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.

A first reading step in which a scale calibrated in a predetermined direction is read by a scanner to generate image data of the scale;
A second reading step of reading a medium on which a pattern is printed by the scanner to generate image data of the medium;
A print position calculating step for calculating a print position for the predetermined direction of the pattern on the medium based on the image data of the scale and the image data of the medium;
A method for calculating a printing position of a pattern on a medium.
According to such a calculation method, the print position in the predetermined direction of the pattern on the medium is calculated based on both the image data of the scale and the image data of the medium. Therefore, the detection error of the scanner itself that can be included when detecting the printing position of the pattern based only on the image data of the pattern can be canceled by using the image data of the scale. As a result, the printing position of the pattern on the medium can be calculated with high accuracy.

In such a calculation method,
The printing position may be indicated as a distance in the predetermined direction from a predetermined reference position to the pattern.
In such a calculation method,
The first reading step and the second reading step are preferably performed in parallel with each other.
According to such a calculation method, since the first reading step and the second reading step are performed in parallel with each other, the detection error of the scanner itself that can be included when detecting the printing position of the pattern is reduced. , The image data of the scale can be surely offset.

In such a calculation method,
In the printing position calculating step,
By correcting the detection position information of the pattern detected based on the image data of the medium based on the detection position information of the scale detected based on the scale image data, the pattern of the pattern It is desirable to calculate the printing position for a predetermined direction.
According to such a calculation method, information on the detection position of the pattern detected based on the image data of the medium is obtained based on information on the detection position of the scale detected based on the image data of the scale. Since the correction is performed, the detection error of the scanner itself that can be included when detecting the printing position of the pattern can be surely offset.

In such a calculation method,
Each scale of the scale is formed with a predetermined theoretical value as a target value for the interval between the scale and another scale adjacent in the predetermined direction,
In the printing position calculating step,
Based on the information on the detection position of the scale and the information on the detection position of the pattern, to obtain relative position information indicating the relative position of the pattern with respect to the scale,
It is preferable to calculate a print position of the pattern in the predetermined direction based on the relative position information and information on the absolute position of the scale based on the theoretical value.
According to such a calculation method, the theoretical value of the interval between the scales is used as information on the absolute position of the scale. Therefore, the procedure can be simplified and the calculation time of the pattern printing position can be shortened by the amount that the absolute position of the scale is not actually measured.

In such a calculation method,
The scale is formed in a linear shape along a direction orthogonal to the predetermined direction,
The pattern is a line printed along a direction orthogonal to the predetermined direction, and a plurality of the lines are printed side by side in the predetermined direction,
In the printing position calculation step, it is preferable that the printing position of the line is calculated for each line as the printing position.
According to such a calculation method, since the direction along the line and the direction along the scale line are aligned, the printing position of the line as the pattern on the medium can be reliably calculated with high accuracy.

In such a calculation method,
The scanner includes a placement surface on which the scale and the medium are placed; a reading carriage that moves in a first direction parallel to the placement surface; and the pattern of the medium or the reading carriage provided on the reading carriage. An image reading sensor for reading the scale of the scale and generating image data may be provided.
In such a calculation method,
It is desirable that the scale and the medium are arranged side by side in the direction intersecting the predetermined direction on the placement surface.
According to such a calculation method, since the scale and the medium are arranged side by side on the mounting surface of the scanner, the images of the scale and the medium are read simultaneously. In other words, the first reading step and the second reading step are performed in parallel with each other, and accordingly, the detection error of the scanner itself that may be included when detecting the printing position of the pattern is expressed as the scale. The image data can be surely offset.
In addition, since the scale and the medium are arranged side by side in a direction crossing the predetermined direction, the printing position of the pattern in the predetermined direction can be reliably calculated by a scale attached to the predetermined direction. It becomes.

In such a calculation method,
The scanner includes a guide member that guides the movement of the reading carriage in the first direction, and a driving source that applies a driving force for moving the reading carriage in the first direction,
In the mounting surface, the scale is placed such that the predetermined direction is directed to the first direction, and the scale is more than the medium with respect to a position in a second direction orthogonal to the first direction. In addition, it is desirable to place the driving force so as to be close to the point of application of the driving force to the reading carriage.
According to such a calculation method, the scale is arranged on the side close to the point of action of the driving force. Therefore, the vibration of the scale side portion of the reading carriage during movement in the first direction is small, so that the image of the scale is read accurately, and the position of the scale on the scale is determined based on the image data. It is detected with high accuracy. As a result, the scale scale is sufficient as a reference for calculating the printing position of the pattern.

In such a calculation method,
Obtaining the reading accuracy of the scanner in the first direction and the reading accuracy in the second direction orthogonal to the first direction;
Based on the obtained reading accuracy in the first direction and the second direction, whether the predetermined direction of the scale to be placed on the placement surface is along the first direction or the second direction It is desirable to decide.
According to such a calculation method, on the basis of the reading accuracy in the first direction and the reading accuracy in the second direction, whether the predetermined direction of the scale is along the first direction or the second direction Decide. Accordingly, the accuracy of the scale scale and the detection position of the pattern of the medium can be increased, and as a result, the printing position of the pattern on the medium can be calculated with high accuracy.

A first reading step of generating a scale-scaled image data by reading a scale scaled in a predetermined direction with a scanner;
A second reading step of reading a medium on which a pattern is printed by the scanner to generate image data of the medium;
A print position calculating step for calculating a print position for the predetermined direction of the pattern on the medium based on the image data of the scale and the image data of the medium;
With
The printing position is indicated as a distance in the predetermined direction from a predetermined reference position to the pattern,
In the printing position calculating step, the information on the detected position of the pattern detected based on the image data of the medium is corrected based on the information on the detected position of the scale detected based on the image data of the scale. By calculating the printing position in the predetermined direction of the pattern,
Each scale of the scale is formed with a predetermined theoretical value as a target value for the interval between the scale and another scale adjacent in the predetermined direction,
In the printing position calculating step, based on the scale detection position information and the pattern detection position information, relative position information indicating a relative position of the pattern with respect to the scale is obtained, and the relative position information, Based on the information on the absolute position of the scale based on a theoretical value, the printing position for the predetermined direction of the pattern is calculated,
The scale is formed in a linear shape along a direction orthogonal to the predetermined direction,
The pattern is a line printed along a direction orthogonal to the predetermined direction, and a plurality of the lines are printed side by side in the predetermined direction,
In the printing position calculation step, the printing position of the line is calculated for each line as the printing position,
The scanner includes a placement surface on which the scale and the medium are placed; a reading carriage that moves in a first direction parallel to the placement surface; and the pattern of the medium or the reading carriage provided on the reading carriage. An image reading sensor for reading the scale of the scale and generating image data,
On the placement surface, the scale and the medium are arranged side by side in a direction intersecting the predetermined direction,
The scanner includes a guide member that guides the movement of the reading carriage in the first direction, and a driving source that applies a driving force for moving the reading carriage in the first direction,
In the mounting surface, the scale is placed such that the predetermined direction is directed to the first direction, and the scale is more than the medium with respect to a position in a second direction orthogonal to the first direction. The method of calculating the printing position of the pattern on the medium, wherein the driving force is placed so as to be close to the point of application of the driving force to the reading carriage.
According to such a calculation method, the effects of the present invention can be achieved most effectively because almost all the effects described above can be achieved.

=== Configuration of Printer 1 ===
<Configuration of Inkjet Printer 1>
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 1 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 the paper S. 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 the 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, 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 S 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 1 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 the head 41 in a predetermined direction (hereinafter referred to as a moving direction). The carriage unit 30 includes a carriage 31 and a carriage motor 32. 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 the paper S. 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, a dot line (raster line) along the moving direction is formed on the paper S by intermittently ejecting ink while the head 41 moves in the moving direction.

  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 S being fed. The optical sensor 54 detects the presence or absence of the paper S by the light emitting unit and the light receiving unit attached to the carriage 31. The optical sensor 54 can detect the position of the end portion of the paper S while being moved by the carriage 31 to detect the width of the paper S. The optical sensor 54 also has a leading edge (an end portion on the downstream side in the transport direction, also referred to as an upper end) and a rear end (an end portion on the upstream side in the transport direction, also referred to as the lower end) of the paper S depending on the situation. It can be detected.

  The controller 60 is a control unit for controlling the printer 1. 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 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 nozzles.

=== Conveying error ===
<Conveying paper S>
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 driving force, the transport roller 23 rotates by a predetermined rotation amount. When the transport roller 23 rotates with a predetermined rotation amount, the paper S is transported with a predetermined transport amount.

The carry amount of the paper S is determined according to the rotation amount of the carry roller 23. Here, it is assumed that when the transport roller 23 makes one revolution, the paper S 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 S is transported by 1/4 inch.
Therefore, if the rotation amount of the transport roller 23 can be detected, the transport amount of the paper S 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.

  For example, when transporting the paper S with a transport amount of 1 inch, the controller 60 drives the transport motor 22 until the rotary encoder 52 detects that the transport roller 23 has made one rotation. In this manner, 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). Carry in.

<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 23 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 the paper S due to the friction of the paper S 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 corresponding to the location of the peripheral surface of the transport roller 23 used during transport. The AC component transport error varies depending on the location of the peripheral surface of the transport roller 23 used during transport. That is, the AC component transport error varies in accordance with the rotational position of the transport roller 23 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 23 is transporting at that 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 S 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 S 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 23 can be considered. For example, when the conveyance roller 23 has an elliptical shape or an egg shape, the distance to the rotation center differs depending on the location of the circumferential surface of the conveyance roller 23. When the paper S 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 23 increases. On the other hand, when the paper S 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 23 decreases.

  Second, the eccentricity of the rotation shaft of the transport roller 23 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 23. For this reason, even if the rotation amount of the conveyance roller 23 is the same, the conveyance amount varies depending on the location of the peripheral surface of the conveyance roller 23.

  Thirdly, a mismatch between the rotation axis of the transport roller 23 and the center of the scale 521 of the rotary encoder 52 is 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>
FIG. 6 is a graph (conceptual diagram) of a transport error that occurs when a paper S having a size of 101.6 mm × 152.4 mm (4 inches × 6 inches) is transported. The horizontal axis of the graph indicates the total transport amount of the paper S. 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 substantially a sine curve regardless of the total transport amount of the paper S. On the other hand, the DC component transport error indicated by the dotted line varies depending on the total transport amount of the paper S due to the influence of the friction of the paper S 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 if the same paper S 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 (transport indicated by the solid line in the graph). Error) 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 23. Therefore, even if the rotational position of the transport roller 23 at the start of transport is different, the transport roller The transport error (DC component transport error) that occurs when 23 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 conveyance amount correction described below, the DC component conveyance error is corrected.

  On the other hand, the DC component transport error varies depending on the total transport amount of the paper S (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 this 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 of correction value setting processing (processing for setting the correction value for correcting the carry amount in the printer 1). 8A to 8C are explanatory diagrams of the state of the correction value setting process. 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 setting program are installed in advance. Then, the correction value setting program executes the correction value setting process of FIG. 7 in cooperation with the printer driver and the scanner driver.

  First, in accordance with an instruction of the correction value setting program, the printer driver transmits print data to the printer 1, and the printer 1 prints a measurement pattern on a test sheet TS (corresponding to a medium) (S101, FIG. 8A). Next, the inspector sets the test sheet TS on the scanner 150. Then, in accordance with the instruction of the correction value setting program, the scanner driver causes the scanner 150 to read the measurement pattern and acquire the image data of the test sheet TS (S102, FIG. 8B). The scanner 150 is set with a test sheet TS and a reference scale SS that is graduated at a predetermined interval, and a scale pattern (hereinafter also referred to as a scale pattern) is read together.

  Then, the correction value setting program analyzes the acquired image data and calculates a correction value (S103). The calculated correction value data (correction data) is transmitted to the printer 1 by the correction value setting program, and the correction value is stored in the memory 63 of the printer 1 (S104, FIG. 8C). The correction value stored in the printer 1 reflects the conveyance characteristics of each printer 1.

  The printer 1 storing the correction value is packed and delivered to the user. When the user prints an image with the printer 1, the printer 1 conveys the paper S based on the correction value and prints the image on the paper S.

=== 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 S in the transport direction, thereby generating a measurement pattern. Print on paper S. 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 41 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 is composed of a plurality of lines. 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 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.

  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 n, 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, in this example, the line Lb2 is formed by using the nozzle # 3 located on the upstream side in the transport direction from the nozzle # 1, thereby increasing the distance between the line Lb1 and the line Lb2 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 Measurement Pattern and Scale Pattern (S102) ===
<Configuration of Scanner 150>
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. 10B is a BB line arrow view in FIG. 10A.

  The scanner 150 includes an upper cover 151, a document table glass 152 on which the document 5 is placed, and a reading carriage 153 that moves in the sub-scanning direction (corresponding to the first direction) while facing the document 5 through the document table glass 152. And a guide member 154 for guiding the reading carriage 153 in the sub-scanning direction, a moving mechanism 155 for moving the reading carriage 153 in the sub-scanning direction, and a scanner controller (not shown) for controlling each part in the scanner 150. ing.

  The reading carriage 153 includes an exposure lamp 157 for irradiating the document 5 with light, and a line sensor 158 for detecting an image of a line in the main scanning direction (corresponding to the second direction) orthogonal to the sub-scanning direction. And an optical device 159 such as a rod lens for guiding the reflected light from the document 5 to the line sensor 158. Note that the broken line inside the reading carriage 153 in FIG. 10A indicates the locus of light.

  As shown in FIG. 10B, the guide member 154 has a pair of rails 154 and 154 that support the reading carriage 153 at both ends 153a and 153b in the main scanning direction. The reading carriage 153 moves in the same direction with a driving force applied in the sub-scanning direction from the moving mechanism 155 with the both ends 153a and 153b being supported.

  The moving mechanism 155 includes a carriage motor 155d, a pair of pulleys 155a and 155b, and a timing belt 155c wound around the pair of pulleys 155a and 155b. The carriage motor 155d is configured by a DC motor or the like, and functions as a drive source for relatively moving the reading carriage 153 along the sub-scanning direction. The timing belt 155c is connected to the carriage motor 155d via a pulley 155a, and a part of the timing belt 155c is connected to the reading carriage 153 by a connecting member 156. Accordingly, the reading carriage 153 is driven by rotation of the carriage motor 155d. Are relatively moved along the sub-scanning direction. The connecting member 156 is provided only at one end 153a in the main scanning direction of the reading carriage 153, and therefore, the driving force of the carriage motor 155d acts on the reading carriage 153 with the one end 153a as an operating point. As a result, the reading carriage 153 is moved in the sub-scanning direction. That is, only the one end portion 153a is an operating point of the driving force, and the other end portion 153b which is the other end portion in the main scanning direction is not an operating point.

  When reading the image of the document 5 by the scanner 150 having such a configuration, first, the operator opens the upper cover 151, places the document 5 on the upper surface 152 a (corresponding to the placement surface) of the document table glass 152, and puts the upper cover 151. close. 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 this example, the scanner 150 reads the measurement pattern of the test sheet TS and the scale pattern of the reference scale SS 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 150. 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 zero point position (position where the reading position is zero) in the sub-scanning direction is exactly 1 inch from the zero point 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 zero point position in the sub-scanning direction is a position that is further 60 μm away from a position that is one inch away from the zero point 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. As described above, in a state where there is an error in the reading position, the line position cannot be accurately measured simply by reading the measurement pattern.
Therefore, in this example, when the test sheet TS is set and the measurement pattern is read by the scanner 150, the reference scale SS is set and the scale pattern of the reference scale SS is also read.

<Reading measurement pattern and scale pattern>
FIG. 12A is an explanatory diagram of the reference scale SS. FIG. 12B is an explanatory diagram showing a state in which the test sheet TS and the reference scale SS are set on the platen glass 152.
The size of the reference scale SS is 10 mm × 300 mm and has a long and thin shape. In the longitudinal direction (corresponding to a predetermined direction) of the reference scale SS, a large number of scales are provided at intervals of 36 dpi, and these scales constitute a scale pattern. Each scale is formed linearly along a direction perpendicular to the longitudinal direction. Since the reference scale SS is repeatedly used, it is not a paper but a resin material such as a PET film. Further, the scale of the reference scale SS is formed with high accuracy by laser processing. In other words, each scale has a predetermined theoretical value (36 dpi) as a target value between the adjacent scales, and has a high precision (for example, a dimension of 1/36 inch ± 0.000027 mm) so that the target value is as much as possible. Formed with tolerance).

  By using a jig (not shown), the test sheet TS and the reference scale SS are set at predetermined positions on the platen glass 152. For example, as shown in FIG. 12B, the placement benchmark BM in the sub-scanning direction is an end edge Eb on the upper surface 152a of the original platen glass 152 on the upstream side in the sub-scanning direction. The direction edge Et and the longitudinal edge Es of the reference scale SS are set to coincide.

  As a result, the reference scale SS is such that the longitudinal direction as the scaled direction is parallel to the sub-scanning direction of the scanner 150, that is, the lines of each scale of the reference scale SS are parallel to the main scanning direction of the scanner 150. Set to be. Further, the test sheet TS set side by side in the main scanning direction of the reference scale SS also has its longitudinal direction parallel to the sub-scanning direction of the scanner 150, that is, each line of the measurement pattern is main-scanned. Set to be parallel to the direction.

  With the test sheet TS and the reference scale SS set in this way, the scanner 150 reads the measurement pattern and the scale 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 scale pattern image is also distorted compared to the actual scale 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 scale pattern is formed at almost equal intervals regardless of the conveyance error of the printer 1, the image of the scale pattern is affected by the error of the reading position of the scanner 150. This is not affected by the transport error.

  Therefore, when calculating the correction value based on the measurement pattern image, the correction value setting program cancels the influence of the reading position error in the measurement pattern image based on the scale pattern image of the reference scale SS. (Cancel).

  Incidentally, here, with reference to FIG. 12B, a preferred arrangement relationship between the test sheet TS and the reference scale SS when the test sheet TS and the reference scale SS are set on the upper surface 152a of the platen glass 152 will be described. As shown in the figure, with respect to the position in the main scanning direction on the upper surface 152a, the reference scale SS is preferably closer to the point of action of the driving force of the reading carriage 153 than the test sheet TS.

  As shown in FIG. 12B, when the driving force of the reading carriage 153 acts only on the one end portion 153a of the reading carriage 153 in the main scanning direction, the vibration generated during the movement of the reading carriage 153 The other end 153b on the opposite side is larger than the one end 153a, which is the point of action of the force, and as a result, the reading accuracy on the other end 153b side may be worse than the one end 153a side. Because. Also, here, the reason why the reading accuracy of the reference scale SS is prioritized, that is, the reference scale SS of the reference scale SS and the test sheet TS is placed on the one end portion 153a side where the reading accuracy does not deteriorate. The reason for the arrangement is that the reference scale SS is used only as a reference, and high-precision position measurement cannot be expected unless the reference is accurate.

=== 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 150 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 setting program. That is, the correction value setting 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 figure, an image indicated by the image data acquired from the scanner 150 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 scale in the image of the scale pattern of the reference scale SS is substantially parallel to the x direction, and each line in the image of the measurement pattern is also substantially parallel to the x 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 read image into two, one image indicates a scale pattern image, and the other image indicates a measurement pattern image. The reason for dividing in this way is that the reference scale SS and the test sheet TS may be tilted separately and set on the scanner 150, so that the tilt 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 1.
θ = tan ⁻¹ {(KY2−KY3) / (KX2−KX3)} Equation 1

  Note that the computer 110 detects not only the inclination of the measurement pattern image but also the inclination of the scale pattern image of the reference scale SS. Since the method of detecting the inclination of the scale pattern image 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 scale pattern image of the reference scale SS is rotationally corrected based on the inclination result of the scale 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 TS passes the transport roller 23 when printing the measurement pattern, the lower end of the test sheet TS may come into contact with the head 41 and the test sheet TS 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 TS is in contact with the head 41 by detecting the inclination during printing of 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 determines that the left interval YL and the right interval YR in the line L1 (the uppermost line) and the line Lb2 (the lowermost line, the line formed after the lower end passes through the transport roller 23). And detect. 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 scale SS and the inclination of the test sheet TS are different, the amount of added margin will be different, and before and after the rotation correction (S133), the line of the measurement pattern line relative to the scale pattern of the reference scale SS The position will shift relatively. Therefore, the computer 110 obtains the margin amount X by the following equation 2 and subtracts the margin amount X from the line position detected in S136, thereby preventing the shift of the position of the measurement pattern line with respect to the scale pattern.
X = (w cos θ−W ′ / 2) × tan θ (Formula 2)

<Detection of Scale Position and Line Position in Scanner Coordinate System (S136)>
Next, the computer 110 detects the scale pattern scale position and the measurement pattern line position 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 a range of an image used when detecting the position of a line. Image data of an image in a range indicated by a dotted line in the drawing is used when detecting the position of the line. FIG. 18B is an explanatory diagram of line position detection. 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 detected, and this barycentric position is set as a line detection position.

  FIG. 19 is an explanatory diagram of the detected positions of the detected lines and scales (note that the detected positions shown in the figure have been made dimensionless by performing a predetermined calculation). Although the scale pattern of the reference scale SS is composed of equally spaced scales, when attention is paid to the position of the center of gravity of each scale of the scale pattern, the detected positions of the detected scales are not evenly spaced. . 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. 20A is an explanatory diagram of calculation of 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 scale of the scale pattern and the jth scale of the scale pattern. In the following description, the detection position (scanner coordinate system) of the i-th line of the measurement pattern is called “S (i)”, and the detection position (scanner coordinate system) of the j-th scale of the scale pattern is “K ( j) ". The interval between the j-1 scale and the jth scale (interval in the y direction) of the scale pattern is called “L”, and the j−1th scale of the scale pattern and the i th 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 3.
H = L (i) / L
= {S (i) -K (j-1)} / {K (j) -K (j-1)} Equation 3
The ratio H indicates the relative position of the i-th line with respect to the scale.

By the way, if the intervals between the scales of the reference scale SS are formed according to the theoretical values, the respective scales should be formed at equal intervals. Therefore, if the position of the first scale of the scale pattern is set to zero as the reference position, the absolute position of any scale of the scale pattern can be calculated. For example, the absolute position of the second scale of the scale pattern is 1/36 inch. Therefore, if the absolute position of the j-th scale of the scale pattern is “J (j)” and the absolute position of the i-th line of the measurement pattern is “R (i)”, R (I) can be calculated.
R (i) = {J (j) −J (j−1)} × H + J (j−1) Equation 4

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 the first measurement pattern based on the magnitude relationship between the value of S (1) (373.768667) and the value of J (2) (309.613250) and the value of J (3) (469.430413). Is located between the second and third scales of the scale pattern. 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 (= {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.

Incidentally, in the above description, the first scale of the scale pattern is set as the reference position, and the absolute position is set to zero. For example, as shown in FIG. 20B, the edge E on the downstream side in the transport direction in the test sheet TS is set as the reference. The absolute position R (i) e from the edge E may be obtained as the position, that is, the absolute position is zero. The R (i) e is obtained by converting the absolute position R (i) obtained by the above equation 4 by the following equation 5.
R (i) e = R (i) + (Rc-R (1)) (5)
Here, Rc is a theoretical value of the distance between the first line L1 of the measurement pattern of the test sheet TS and the edge E of the test sheet TS, as shown in FIG. 20B. R (1) is the absolute position of the line L1 obtained by the above equation 4.

<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 does not include an 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 distance between two adjacent 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 transport amount, if the correction value C calculated based on the interval between two adjacent lines in the measurement pattern is applied as it is, the transport error is caused by the influence of the AC component transport 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 this example, in order to correct only the DC component transport error, the correction for correcting the DC component transport error is performed by averaging four correction values C as shown in the following equation (6). The amount Ca is calculated.
Ca (i) = {C (i-1) + C (i) + C (i + 1) + C (i + 2)} / 4
...... Formula 6

Here, the reason why the correction value Ca for correcting the DC component transport error can be calculated by the above equation 6 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 6 for calculating the correction value Ca has a meaning as the following equation 7.
Ca (i) = [25.4 mm− {R (i + 3) −R (i−1)}] / 4 Equation 7

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. For this reason, the correction value Ca (i) is a value for correcting ¼ of a transport error that occurs when the paper S is transported by 1 inch (a transport amount for one rotation of the transport roller 23). A transport error that occurs when the paper S is transported by 1 inch is a DC component transport error, and this transport error does not include an AC component transport error.
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 1 is stored in the memory 63 for each manufactured printer. The printer 1 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 1, 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. I 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 S) matches the boundary position on the upper end side of the application range of the correction value Ca (i), and the nozzle # 90 after the transport operation The position coincides with 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 conveyance motor 22 with the target value obtained by adding the correction value Ca (i) from the initial target conveyance amount F, and loads the paper S. Transport.

  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 S.

  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 value obtained by adding the correction value from the initial target carry amount F to carry the paper S.

  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 value obtained by adding the correction value from the initial target carry amount F to carry the paper S.

  As described above, when the controller 60 corrects the initial target transport amount F and controls the transport unit 20 based on the corrected target transport amount F, the actual transport amount is corrected to the initial target transport amount F. Then, 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.

=== Other Embodiments ===
<Arrangement direction of reference scale SS and test sheet TS on platen glass 152>
In the above-described embodiment, as shown in FIG. 12B, when the reference scale SS and the test sheet TS are placed on the platen glass 152, the direction of the scale line of the reference scale SS and the direction of the line of the test sheet TS However, the arrangement direction is not limited to this and may be reversed. That is, the direction of the scale line of the reference scale SS and the direction of the line of the test sheet TS may be placed on the platen glass 152 so as to be along the sub-scanning direction.
However, when the reading accuracy of the scanner 150 is different between the sub-scanning direction and the main scanning direction, it is desirable to determine the arrangement direction in consideration of the anisotropy of the reading accuracy.

  For example, when the graph sheet HS as shown in the upper part of FIG. 24 is read by the scanner 150, the image of the read image data is a straight line along the main scanning direction as shown in the middle left part of FIG. However, when the lines in the sub-scanning direction are wavy (that is, when the reading accuracy in the sub-scanning direction is worse than that in the main scanning direction), as shown in the lower left part of FIG. The test sheet TS may be arranged so that the TS line is along the main scanning direction. In this case, it goes without saying that the reference scale SS is arranged so that the longitudinal direction thereof faces the sub-scanning direction.

  On the other hand, in the image data of the graph paper HS read by the scanner 150, the line along the sub-scanning direction is linear as shown in the middle right side of FIG. 24, but the lines in the main scanning direction are wavy. In this case (that is, when the reading accuracy in the main scanning direction is worse than that in the sub-scanning direction), as shown in the lower right side of FIG. 24, the test sheet TS is aligned along the sub-scanning direction. It is good to arrange TS. In this case, it goes without saying that the reference scale SS is arranged so that the longitudinal direction thereof faces the main scanning direction.

  In this way, the accuracy of the detection position S (i) in the scanner coordinate system of the line of the test sheet TS and the detection position K (j) in the scanner coordinate system of the scale of the reference scale SS can be improved. As a result, the absolute position R (i) of the line of the test sheet TS can be calculated with high accuracy.

=== Summary ===
(1) The “method for calculating the printing position of the pattern on the medium” according to the above-described embodiment is as follows. (A) The reference scale SS calibrated in a predetermined direction (longitudinal direction) is read by the scanner 150 and the reference scale A first reading step for generating SS image data (corresponding to step S102 in FIG. 7), and (B) a test sheet TS printed with a line is read by the same scanner 150 as the scanner 150 and an image of the test sheet TS Based on the second reading step (corresponding to step S102 in FIG. 7) for generating data, and (C) the image data of the reference scale SS and the image data of the test sheet TS, the predetermined direction of the line on the test sheet TS A printing position calculation step (step S136 in FIG. 13 and It includes a corresponding) to 137.
Then, based on both the image data of the reference scale SS and the image data of the test sheet TS, the absolute position R (i) in the predetermined direction of each line on the test sheet TS is calculated, so that only the image data of the line The detection error of the scanner 150 itself that can be included when the absolute position R (i) of the line is obtained based on the above can be canceled by using the image data of the reference scale SS. As a result, the absolute position R (i) of the line on the test sheet TS can be calculated with high accuracy.

(2) In the above-described embodiment, the reference position at which the absolute position R (i) is zero is the position of the first scale of the reference scale SS or the edge E on the downstream side in the conveyance direction of the test sheet TS. Position. When the reference position is the former, the absolute position R (i) indicates the distance in the predetermined direction from the position of the first scale to each line, while in the latter case, the edge E The distance in the predetermined direction from each line to each line is shown.

(3) In the above-described embodiment, step S102 in FIG. 7 corresponds to the first reading step and the second reading step. Therefore, the first reading step and the second reading step are performed in parallel with each other, and as a result, the detection error of the scanner itself that can be included in detecting the absolute position R (i) of the line is represented by the reference scale SS. The image data can be surely offset.

(4) In the above-described embodiment, steps S136 and S137 in FIG. 13 correspond to the print position calculation step. In step S137, the information on the detection position S (i) of each line detected based on the image data of the test sheet TS is converted into the image data of the reference scale SS as shown in the above-described Expression 3 and Expression 4. The absolute position R (i) with respect to the predetermined direction of each line is calculated by performing correction based on the information of the detected positions K (j) and K (j−1) of the scale detected based on the above. Therefore, the detection error of the scanner itself that can be included when obtaining the absolute position R (i) of each line can be reliably canceled.

(5) In the above-described embodiment, each scale of the reference scale SS is formed such that the distance between the scale and another scale adjacent in the predetermined direction is a predetermined theoretical value (1/36 inch) as a target value. ing. In step S137 of the above-described print position calculation step (corresponding to steps S136 and S137 in FIG. 13), information on the scale detection positions K (j) and K (j−1) is obtained as shown in Equation 3 above. And, based on the information of the detection position S (i) of each line, the ratio H indicating the relative position of each line with respect to the scale is obtained, and in the next step S137, the ratio H Based on the information and information on the absolute position J (j), J (j-1) of the scale based on the theoretical value (1/36 inch), the absolute position R (i) of each line in the predetermined direction is obtained. calculate.
Here, since the information based on the theoretical value of the scale interval is used as the information on the absolute scale positions J (j) and J (j−1), the absolute scale positions J (j) and J (j− The procedure can be simplified as much as 1) is not actually measured, and the calculation time of the absolute position R (i) of the line can be shortened.

(6) In the above-described embodiment, as shown in FIG. 12B, the scale of the reference scale SS is formed in a linear shape along a direction orthogonal to the predetermined direction (longitudinal direction of the reference scale SS). The test sheet TS is printed along a direction orthogonal to the predetermined direction, and a plurality of lines are printed in the predetermined direction. In the printing position calculation step (corresponding to steps S136 and S137 in FIG. 13), the absolute position R (i) of the line is calculated for each line.
Therefore, since the direction along the line and the direction along the scale line are both the same direction and are aligned, the scale of the reference scale SS ensures the absolute position R (i) of the line on the test sheet TS. It becomes possible to calculate with high accuracy.

(7) In the above-described embodiment, as shown in FIGS. 10A and 10B, the scanner 150 includes the upper surface 152a of the document table glass 152 on which the reference scale SS and the test sheet TS are placed, and is parallel to the upper surface 152a. A reading carriage 153 that moves in the sub-scanning direction, and a line sensor 158 that is provided on the reading carriage 153 and reads the scale of the test sheet TS or the scale of the reference scale SS to generate image data are provided.

(8) In the above-described embodiment, the reference scale SS and the test sheet TS are orthogonal to the predetermined direction (longitudinal direction of the reference scale SS) on the upper surface 152a of the document table glass 152, as shown in FIG. 12B. Arranged side by side. Therefore, the images of the reference scale SS and the test sheet TS are read simultaneously. That is, the first reading step and the second reading step are performed in parallel with each other in step S102 of FIG.
As a result, the detection error of the scanner itself that can be included when obtaining the absolute position R (i) of the line of the test sheet TS can be reliably canceled by the image data of the reference scale SS. Further, as shown in FIG. 12B, the reference scale SS and the test sheet TS are arranged side by side in a direction orthogonal to the predetermined direction (longitudinal direction of the reference scale SS). The scale makes it possible to reliably calculate the absolute position R (i) of the line in the predetermined direction.

(9) In the above-described embodiment, as shown in FIG. 10B, the scanner 150 moves in the sub-scanning direction with respect to the rails 154 and 154 that guide the movement of the reading carriage 153 in the sub-scanning direction. A carriage motor 155d for providing a driving force for the Then, as shown in FIG. 12B, on the upper surface 152a of the document table glass 152, the reference scale SS is placed so that the predetermined direction, which is the longitudinal direction thereof, is directed to the sub-scanning direction. The reference scale SS is placed closer to the point of action of the driving force on the reading carriage 153 than the test sheet TS.
Here, in general, the vibration when the reading carriage 153 moves in the sub-scanning direction is smaller in the portion closer to the operating point of the driving force than in the far portion. Therefore, according to the above arrangement, the vibration of the end 153a on the reference scale SS side in the reading carriage 153 is small, so that the image of the reference scale SS is read accurately, and the reference scale SS is based on the image data. The scale detection positions K (j) and K (j-1) are detected with high accuracy. As a result, the scale of the reference scale SS is sufficient as a reference for calculating the absolute position R (i) of the line.

(10) In the above embodiment, as shown in FIG. 24, the reading accuracy of the scanner 150 in the sub-scanning direction and the reading accuracy of the scanner 150 in the main scanning direction are obtained, and the obtained reading in the sub-scanning direction and the main scanning direction is obtained. Based on the accuracy, it is determined whether the longitudinal direction of the reference scale SS when being placed on the upper surface 152a of the platen glass 152 of the scanner 150 is along the sub-scanning direction or the main scanning direction. Therefore, the accuracy of the scales of the reference scale SS and the detection positions K (j) and S (i) of the test sheet TS can be improved, and as a result, the absolute position R (i of the line on the test sheet TS. ) Can be calculated with high accuracy.

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 of a correction value setting process. 8A to 8C are explanatory diagrams of the state of the correction value setting process. It is explanatory drawing of the mode of printing of the pattern for a measurement. 10A is a longitudinal sectional view of the scanner 150, and FIG. 10B is a view taken along the line BB in FIG. 10A. 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 a range of an image used when detecting the position of a line. FIG. 18B is an explanatory diagram of line position detection. It is explanatory drawing of the position of the detected line. It is explanatory drawing of calculation of absolute position R (i) of the i-th line of the pattern for a measurement. It is explanatory drawing of calculation of absolute position R (i) of the i-th line when edge E of the conveyance direction downstream of test sheet TS is made into a reference position. 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 other embodiment.

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, 152a top surface,
153 reading carriage, 153a one end, 153b other end,
154 rail, 155 moving mechanism,
155a pulley, 155b pulley, 155c timing belt,
155d carriage motor, 156 connecting member,
157 exposure lamp, 158 line sensor, 159 optical equipment,
TS test sheet, SS reference scale

Claims (11)

A first reading step in which a scale calibrated in a predetermined direction is read by a scanner to generate image data of the scale;
A second reading step of reading a medium on which a pattern is printed by the scanner to generate image data of the medium;
A print position calculating step for calculating a print position for the predetermined direction of the pattern on the medium based on the image data of the scale and the image data of the medium;
A method for calculating a printing position of a pattern on a medium. In the calculation method of the printing position of the pattern on the medium according to claim 1,
The method for calculating a printing position of a pattern on a medium, wherein the printing position is indicated as a distance in a predetermined direction from a predetermined reference position to the pattern. In the calculation method of the printing position of the pattern on the medium according to claim 1 or 2,
The method for calculating a printing position of a pattern on a medium, wherein the first reading step and the second reading step are performed in parallel with each other. In the calculation method of the printing position of the pattern on the medium according to any one of claims 1 to 3,
In the printing position calculating step,
By correcting the detection position information of the pattern detected based on the image data of the medium based on the detection position information of the scale detected based on the scale image data, the pattern of the pattern A printing position calculation method for a pattern on a medium, wherein a printing position for a predetermined direction is calculated. In the calculation method of the printing position of the pattern on the medium according to claim 4,
Each scale of the scale is formed with a predetermined theoretical value as a target value for the interval between the scale and another scale adjacent in the predetermined direction,
In the printing position calculating step,
Based on the information on the detection position of the scale and the information on the detection position of the pattern, to obtain relative position information indicating the relative position of the pattern with respect to the scale,
A printing position calculation method for a pattern on a medium, wherein a printing position for the predetermined direction of the pattern is calculated based on the relative position information and information on an absolute position of the scale based on the theoretical value. . In the calculation method of the printing position of the pattern on the medium according to any one of claims 1 to 5,
The scale is formed in a linear shape along a direction orthogonal to the predetermined direction,
The pattern is a line printed along a direction orthogonal to the predetermined direction, and a plurality of the lines are printed side by side in the predetermined direction,
In the printing position calculation step, the printing position of the line on the medium is calculated as the printing position for each line. In the calculation method of the printing position of the pattern on the medium according to any one of claims 1 to 6,
The scanner includes a placement surface on which the scale and the medium are placed; a reading carriage that moves in a first direction parallel to the placement surface; and the pattern of the medium or the reading carriage provided on the reading carriage. An image reading sensor for reading the scale of the scale and generating image data, and a method for calculating a printing position of a pattern on a medium. In the calculation method of the printing position of the pattern on the medium according to claim 7,
A method for calculating a printing position of a pattern on a medium, wherein the scale and the medium are arranged side by side in a direction crossing the predetermined direction on the placement surface. In the calculation method of the printing position of the pattern on the medium according to claim 8,
The scanner includes a guide member that guides the movement of the reading carriage in the first direction, and a driving source that applies a driving force for moving the reading carriage in the first direction,
In the mounting surface, the scale is placed such that the predetermined direction is directed to the first direction, and the scale is more than the medium with respect to a position in a second direction orthogonal to the first direction. The method of calculating the printing position of the pattern on the medium, wherein the driving force is placed so as to be close to the point of application of the driving force to the reading carriage. In the calculation method of the printing position of the pattern on the medium according to claim 7 or 8,
Obtaining the reading accuracy of the scanner in the first direction and the reading accuracy in the second direction orthogonal to the first direction;
Based on the obtained reading accuracy in the first direction and the second direction, whether the predetermined direction of the scale to be placed on the placement surface is along the first direction or the second direction A method for calculating a printing position of a pattern on a medium. A first reading step in which a scale calibrated in a predetermined direction is read by a scanner to generate image data of the scale;
A second reading step of reading a medium on which a pattern is printed by the scanner to generate image data of the medium;
A print position calculating step for calculating a print position for the predetermined direction of the pattern on the medium based on the image data of the scale and the image data of the medium;
With
The printing position is indicated as a distance in the predetermined direction from a predetermined reference position to the pattern,
In the printing position calculating step, the information on the detected position of the pattern detected based on the image data of the medium is corrected based on the information on the detected position of the scale detected based on the image data of the scale. By calculating the printing position in the predetermined direction of the pattern,
Each scale of the scale is formed with a predetermined theoretical value as a target value for the interval between the scale and another scale adjacent in the predetermined direction,
In the printing position calculating step, based on the scale detection position information and the pattern detection position information, relative position information indicating a relative position of the pattern with respect to the scale is obtained, and the relative position information, Based on the information on the absolute position of the scale based on a theoretical value, the printing position for the predetermined direction of the pattern is calculated,
The scale is formed in a linear shape along a direction orthogonal to the predetermined direction,
The pattern is a line printed along a direction orthogonal to the predetermined direction, and a plurality of the lines are printed side by side in the predetermined direction,
In the printing position calculation step, the printing position of the line is calculated for each line as the printing position,
The scanner includes a placement surface on which the scale and the medium are placed; a reading carriage that moves in a first direction parallel to the placement surface; and the pattern of the medium or the reading carriage provided on the reading carriage. An image reading sensor for reading the scale of the scale and generating image data,
On the placement surface, the scale and the medium are arranged side by side in a direction intersecting the predetermined direction,
The scanner includes a guide member that guides the movement of the reading carriage in the first direction, and a driving source that applies a driving force for moving the reading carriage in the first direction,
In the mounting surface, the scale is placed such that the predetermined direction is directed to the first direction, and the scale is more than the medium with respect to a position in a second direction orthogonal to the first direction. The method of calculating the printing position of the pattern on the medium, wherein the driving force is placed so as to be close to the point of application of the driving force to the reading carriage.

Images