JP7363087B2 - printer - Google Patents

Description

The present invention relates to printers such as label printers.

Conventionally, as a type of printer, a label printer is known that uses a roll of long printing paper wound around it and prints images of each page arranged in the longitudinal direction on the printing paper that is fed out from the roll. Printing paper includes plain paper, thermal paper, and label paper in which labels are pasted on a long release liner at predetermined intervals in the longitudinal direction.

Label printers are often used to finish printing in the middle of a roll, replace it with another roll, and start the next print, rather than using the roll from start to finish all at once. Therefore, when starting the next print, cueing is required to set the print start position.

However, for rolls that have been used halfway, the leading edge of the printing paper is not necessarily cut in a straight line perpendicular to the transport direction (longitudinal direction), and the leading edge of the printing paper may be cut by the user's hand. It may be in a broken state. Therefore, multiple paper detection sensors are arranged side by side in the width direction of the print paper (print paper) to detect the position of the leading edge of the print paper across the width direction, and based on the detection results, the leading edge of the print paper is positioned perpendicular to the transport direction. A configuration has been proposed in which the cutting position with a cutter is determined in order to make a straight line.

Japanese Patent Application Publication No. 2006-181834

The technology for detecting the position of the leading edge of print paper is not limited to the proposed configuration, and can also be used for cueing. However, if the leading edge of the printing paper is torn by the user's hand, the surface of the printing paper may be torn off thinly, or only the release liner remains and there is no label. be. In this case, a transmissive or reflective photosensor that is normally used as a paper detection sensor cannot determine the condition of the surface of the printing paper, so there is a risk that the print start position will be set at a position that is not suitable for printing.

SUMMARY OF THE INVENTION An object of the present invention is to provide a printer that can correctly set the print start position to the head position of the usable area of the print paper, regardless of the surface condition of the print paper.

In order to achieve the above object, a printer according to the present invention includes a transport unit that transports a long printing paper, a drive unit that drives the transport unit, and a printer that prints an image on the printing paper that is transported by the transport unit. a reading unit capable of reading the entire width of the printing paper in the width direction orthogonal to the conveying direction of the printing paper, and a control unit, the control unit configured to perform the same feeding as when printing by the printing unit. a first drive process that issues a command to the drive unit to drive the transport unit in the direction; and after issuing the command by the first drive process, issues a command to the reading unit to start reading; A first reading process for reading the printing paper, and a driving direction of the transport unit based on the image data read by the reading unit in the first reading process, the feeding direction or the rewinding direction opposite to the feeding direction. a second drive process that instructs the drive unit to drive the transport unit in the determined direction; and after issuing the command by the second drive process, instructs the reading unit to start reading; a second reading process that causes the reading unit to read the printing paper; and a search for the leading position of the usable area of the printing paper based on the image data read by the reading unit in the second reading process. A head search process to be determined is executed.

According to this configuration, the printing paper is read by the reading section, and the driving direction of the conveying section by the driving section is determined based on the image data obtained by the reading. Then, while the printing paper is being transported in the transporting direction corresponding to the determined drive direction, the printing paper is read by the reading section, and the leading position of the usable area of the printing paper is searched. Based on this search result, the printing start position of the image by the printing unit can be correctly set to the leading position of the usable area of the printing paper, regardless of the surface condition of the printing paper.

According to the present invention, the printing start position of an image by the printing unit can be correctly set at the beginning position of the usable area of the printing paper, regardless of the surface condition of the printing paper.

1 is a schematic cross-sectional view showing the internal configuration of a label printer according to an embodiment of the present invention. FIG. 2 is a block diagram showing the electrical configuration of a label printer. 3 is a flowchart showing the flow of cue processing. 7 is a flowchart showing the flow of rectangular area processing. 3 is a flowchart showing the flow of block type determination processing. FIG. 3 is an illustrative plan view showing a state in which a portion of the sheet upstream in the conveyance direction from the leading edge of the sheet is located at the reading position of the reading device. FIG. 3 is an illustrative plan view showing a state where no paper is present at the reading position of the reading device. FIG. 3 is an illustrative plan view showing a state in which the leading edge of the paper is located at the reading position of the reading device. FIG. 7 is a diagram for explaining a case where the leading position of a usable area on a sheet of paper is searched for while the sheet of paper is being conveyed in the opposite direction. FIG. 7 is a diagram for explaining a case where the leading position of a usable area on a sheet of paper is searched for while the sheet of paper is being conveyed in the forward direction. FIG. 7 is a diagram for explaining a modified example of the method of dividing into blocks.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

<Label printer>
FIG. 1 shows a label printer 1 that is an example of a printer. The label printer 1 includes a casing 11 that forms its outer shell.

For use in the following description, one side of the housing 11 will be defined as the "front side" and the opposite side will be defined as the "rear side." Then, the left and right sides are defined based on the state in which the label printer 1 is viewed from the "front side." The direction perpendicular to both the front-rear direction and the left-right direction is the "up-down direction", and the "upper side" and the "lower side" are based on the state in which the label printer 1 is installed on a horizontal surface.

A discharge port 12 for discharging paper P (an example of printing paper) is formed on the front side surface of the housing 11 . The discharge port 12 is a rectangular opening extending in the left-right direction, and communicates between the inside and outside of the housing 11 .

A roll holder 13 that holds a paper roll R is provided inside the housing 11. The paper roll R is a roll of paper P wound around a roll core. The paper P may be a label paper (die-cut label paper) having a large number of print areas set side by side in its longitudinal direction, or may be continuous paper such as plain paper or thermal paper that does not have such print areas. There may be. In addition, label paper may be a long sheet of plain paper with a frame pre-printed on the printing surface to divide the printing area, or a sheet of adhesive paper overlaid on a long sheet of release paper and the adhesive The label may be formed by cutting out labels from paper and arranging them in the longitudinal direction. In the latter case, the printing surface of each label (the surface opposite to the adhesive surface) is the printing area. When the paper P is label paper, the paper P is wound around a roll core so that the printed surface faces outward. The roll holder 13 has a substantially cylindrical shape, and the roll core of the paper roll R is fitted onto the roll holder 13 so that the paper roll R is held by the roll holder 13 .

Further, within the housing 11, a direction changing roller 14 is provided at the rear and upper part of the roll holder 13. A conveyance path 15 through which the paper P is conveyed is provided in front of the direction change roller 14 . The conveyance path 15 extends toward the front from a position above the direction change roller 14 , and its front end is connected to the discharge port 12 . The paper P is pulled out from the paper roll R toward the rear side of the direction change roller 14 , is changed in direction to the front side by running along the circumferential surface of the direction change roller 14 , and is directed along the conveyance path 15 toward the discharge port 12 . will be passed.

On the conveyance path 15, conveyance rollers 16 and 17 (an example of a conveyance section) for conveying the paper P are provided. One of the conveyance rollers 16 is arranged in front of the direction change roller 14 with a space therebetween. The other conveyance roller 17 is arranged on the rear side of the discharge port 12 and in front of the conveyance roller 16 with a space therebetween. With the paper P being passed between the conveyance rollers 16 and 17, the power generated by the forward rotation of the motor M (see FIG. 2) is transmitted to the conveyance rollers 16 and 17, and the conveyance rollers 16 and 17 rotate. As a result, the paper P is transported along the transport path 15 in the delivery direction toward the discharge port 12 . Further, the power generated by the reverse drive of the motor M is transmitted to the roll holder 13, and the roll core of the paper roll R is rotated in the opposite direction to the direction in which the paper P is transported in the delivery direction, so that the paper P is rotated in the transport direction. It is transported in the reverse rewinding direction. When the paper P is transported in the rewinding direction, the transport rollers 16 and 17 are in a freely rotating state.

Between the conveyance rollers 16 and 17, a print head 21 (an example of a printing section) and a reading device 22 (an example of a reading section) are arranged in this order in the sending direction.

The print head 21 is arranged facing the conveyance path 15 from above. The print head 21 prints an image on the printing surface of the paper P conveyed through the conveyance path 15, for example, by an inkjet recording method. A position facing the print head 21 in the vertical direction is a printable position where printing by the print head 21 is possible, and the print head 21 prints an image on a portion of the printing surface of the paper P located at the printable position.

The reading device 22 is disposed on the downstream side of the print head 21 in the sending direction, facing the transport path 15 from above. The reading device 22 uses, for example, a CIS (Contact Image Sensor) to read the printed surface of the paper P conveyed through the conveyance path 15. Specifically, although not shown in the drawings, the reading device 22 has a built-in light source, a rod lens array, and a linear image sensor, and a line-shaped light is irradiated from the light source onto the printed surface of the paper P. The reflected light passes through the rod lens array and enters the linear image sensor. As a result, one line of the document is read in the main scanning direction at the reading position of the reading device 22. A linear image sensor has a configuration in which a plurality of image sensors (image sensors) are arranged in a line in the main scanning direction, and image data read by each image sensor becomes image data (pixel value) of one pixel.

Further, a platen 23 is provided between the conveyance rollers 16 and 17. The platen 23 is arranged to face the print head 21 and the reading device 22 from below with the transport path 15 in between. The platen 23 has a flat surface facing the print head 21 and the reading device 22, that is, an upper surface, and supports the paper P from below. The upper surface of the platen 23 is black. The width of the reading line of the reading device 22 in the main scanning direction is set to be larger than the width of the paper P in the main scanning direction.

<Main parts of electrical configuration>
As shown in FIG. 2, the label printer 1 includes a CPU (Central Processing Unit) 31, a ROM (Read Only Memory) 32, and a RAM (Random Access Memory) 33.

The ROM 32 is composed of a rewritable nonvolatile memory such as a flash memory. The ROM 32 stores programs executed by the CPU 31 (an example of a control unit), various data, and the like. The CPU 31 controls the print head 21 and the reading device 22 by executing a program, and also controls the motor M, which is an example of a drive unit that drives the conveyance rollers 16 and 17. The RAM 33 is a volatile memory such as DRAM (Dynamic Random Access Memory), and is used as a work area when the CPU 31 executes a program.

Further, the RAM 33 constitutes a step number counter. The step number counter increments the step number (+1) each time the motor M is driven one step. The CPU 31 can control the position of the paper P by controlling the drive of the motor M based on the number of steps counted by the step number counter.

The label printer 1 includes a communication interface 34 for communicating with an external terminal such as a PC (Personal Computer). The communication interface 34 may be configured to perform wired communication with an external terminal via a USB (Universal Serial Bus) cable or LAN (Local Area Network) cable, or may be configured to communicate wirelessly via radio waves or the like. Good too.

When the label printer 1 executes a print job to print an image such as a shipping label on paper P, for example, an external terminal communicably connected to the label printer 1 generates printer control commands for each page. be done. The printer control command is a command that controls the label printer 1 to print an image, and is a command that describes print data including information such as the position of characters, character type, and position of figures in the image to be printed in a page description language. It is something. If the print job is to print images over multiple pages on paper P, printer control commands for each of the multiple pages are generated. When a printer control command is generated on an external terminal, the function of the printer driver installed on the external terminal generates print control commands for all pages in order, starting with the printer control command for the first page, following the command to execute the print job. is sent to the label printer 1.

<Cueing process>
When the CPU 31 of the label printer 1 receives an instruction to execute a print job from an external terminal via the communication interface 34, the CPU 31 executes the cue processing shown in FIG. 3.

In the cueing process, the CPU 31 issues a command to the motor M (a motor driver that drives the motor M) to drive the conveyance rollers 16 and 17 in the sending direction. By driving the conveyance rollers 16 and 17 in the sending direction, the conveyance direction of the paper P becomes the forward direction from the paper roll R toward the discharge port 12 (S11).

While the paper P is being transported in the forward direction, the CPU 31 executes rectangular area processing (S12).

In the rectangular area processing, as shown in FIG. 4, the CPU 31 issues a command to the reading device 22 to start reading, and in response to the command, the reading device 22 starts reading (S121). Thereafter, the CPU 31 determines whether or not an area of length A has been read by the reading device 22 in the sub-scanning direction parallel to the conveyance direction of the paper P (S122). The CPU 31 causes the reading device 22 to continue reading until it is determined that the paper P has been conveyed over a length A in the forward direction and an area of length A in the sub-scanning direction has been read by the reading device 22 (S122: NO).

When the CPU 31 determines that the area of length A in the sub-scanning direction has been read by the reading device 22 (S122: YES), the CPU 31 detects edges on both sides of the sheet P in the width direction from the image data read by the reading device 22. (S123). The width direction is a direction perpendicular to the conveyance direction of the paper P, and is a direction that coincides with the main scanning direction in reading by the reading device 22. Since the surface color of the paper P is white, and the surface color of the platen 23 is black, the CPU 31, for example, identifies the portion where the image data value (pixel value) crosses the threshold value in the main scanning direction as an edge. Detect as position. Note that if the paper P does not exist in a position that can be read by the reading device 22 and the edge of the paper P is not detected by the CPU 31, for example, the endmost pixels on both sides in the width direction in the area read by the reading device 22 Detected as an edge.

After that, the CPU 31 divides the number of image data included between the edges on both sides in the main scanning direction by a predetermined number of 2 or more, and determines the divided value as the length B of one block in the main scanning direction. Subsequently, the CPU 31 divides the image data read by the reading device 22 into a predetermined number of blocks arranged in rows in the main scanning direction, based on the length B of one block in the main scanning direction (S124).

Then, the CPU 31 selects all the areas included in a rectangular area (hereinafter referred to as "target rectangular area") whose length in the sub-scanning direction is length A and whose length in the main scanning direction is length B x a predetermined number. For each block, block type determination processing is executed to determine whether the block belongs to a block with paper, a block without paper, or a damaged block (S125). Details of the block type determination process will be described later.

Each time the block type determination process is executed for one block, the CPU 31 determines whether the block type determination process has been executed for all blocks included in the target rectangular area (S126).

If the block type determination of all blocks has not been completed (S126: NO), the CPU 31 repeats the block type determination process (S125). When the determination of the block types of all blocks is completed (S126: YES), the CPU 31 determines whether all blocks included in the target rectangular area are blocks with paper (S127). If all the blocks are blocks with paper (S127: YES), the CPU 31 further determines whether the difference between the average values of the pixel values of each block is greater than or equal to a certain value (S128). If the difference between the average pixel values of each block is more than a certain value (S128: YES), the surface condition of the paper P is not uniform (the surface is thinly torn, dirt, scratches, holes, etc.). Therefore, the CPU 31 changes the determination that the block with the maximum or minimum average value is a block with paper in the block type determination process to determine that the block with the maximum or minimum average value belongs to the damaged block (S129). This makes it possible to determine the printing start position taking into consideration the surface condition. After changing the determination, the CPU 31 ends the rectangular area processing. Also, if all the blocks included in the target rectangular area are not blocks with paper (S127: NO), or if all the blocks are blocks with paper, but the difference between the average values of pixel values of each block is less than a certain value (S128: NO), the CPU 31 ends the rectangular area processing without changing the block type determination.

In the block type determination process, for example, as shown in FIG. 5, the CPU 31 calculates the average value of pixel values included in the block (S1251). The CPU 31 determines whether the calculated average value is greater than or equal to the first threshold (S1252).

When the pixel value takes a value in the range of "0" (black) to "255" (white) and the paper P is blank, the first threshold value is set to a value close to the maximum value "255". When the reading area corresponding to the block to be determined is on the front surface of paper P, each pixel value included in that block is a value close to the maximum value "255", for example, a value in the range of "221" to "255". Therefore, the average value of the pixel values included in the block also becomes a value close to the maximum value "255". Therefore, if the average value of the pixel values included in the block is equal to or greater than the first threshold value (for example, 221) (S1252: YES), the CPU 31 determines that the block is a sheet of paper that is composed of image data obtained by reading the front surface of the sheet of paper P. It is determined that the block is a valid block (S1253). Note that the first threshold value can be changed as appropriate depending on the background color of the paper P.

If the average value of the pixel values included in the block is not greater than or equal to the first threshold (S1252: NO), that is, if the average value is less than the first threshold, the CPU 31 determines whether the average value is less than the second threshold. is determined (S1254). The second threshold is set to a value smaller than the first threshold and close to the minimum value "0" of pixel values. When the reading area corresponding to the block to be determined is the surface of the platen 23, each pixel value included in that block is a value close to the minimum value "0", for example, a value in the range of "1" to "100". Therefore, the average value of the pixel values included in the block also becomes a value close to the minimum value "0". Furthermore, if the reading area corresponding to the block to be determined includes the leading edge (cut edge) of the paper P, in other words, if the reading area includes both the surface of the paper P and the surface of the platen 23, the block The average value of the included pixel values is an intermediate value in the range of "0" to "255", for example, a value in the range of intermediate values "101" to "220". Therefore, if the average value of the pixel values included in the block is less than the second threshold (for example, 101) (S1254: YES), the CPU 31 determines that the block is composed of the image data obtained by reading the surface of the platen 23. It is determined that the block is a blank block (S1255). Further, if the average value of the pixel values included in the block is not less than the second threshold (S1254: NO), that is, if the average value of the pixel values is less than the first threshold and greater than or equal to the second threshold, the CPU 31 determines that the block is It is determined that the area including the leading edge of the paper P is a damaged block composed of image data read (S1256).

Note that the constant value of the difference between the average values of pixel values of each block in the rectangular area processing is about "20" in accordance with the example of the block type determination processing.

After completing the rectangular area processing, the CPU 31 returns to the cueing process shown in FIG. 3 and determines whether all blocks in the target rectangular area are paper blocks (S13). When all the blocks are blocks with paper, as shown in FIG. 6, a portion of the paper P upstream of the leading edge of the paper P in the transport direction is located at the reading position of the reading device 22. In order to detect the leading edge of the paper P in this state, the paper P must be transported in the opposite direction to the forward direction, that is, in the direction from the discharge port 12 to the paper roll R. On the other hand, if all the blocks in the target rectangular area are not blocks with paper, as shown in FIG. 7, there is no paper P at the reading position of the reading device 22, or as shown in FIG. , the leading edge of the paper P is located at the reading position of the reading device 22. Therefore, in order to detect the leading edge of the paper P from these conditions, the paper P must be transported in the forward direction.

If the CPU 31 determines that all blocks in the target rectangular area are blocks with paper (S13: YES), the CPU 31 causes the motor M to move the transport rollers 16 and 17 in the opposite direction to the feeding direction so that the paper P is transported in the opposite direction. A command to drive in the rewinding direction is issued (S14). When the paper P starts to be transported in the reverse direction, the CPU 31 newly executes rectangular area processing in order to search for the leading position of the usable area on the paper P (S15). Then, the CPU 31 determines whether or not the target rectangular area in the new rectangular target process includes a paperless block or a damaged block based on the result of the newly executed rectangular area process. If the target rectangular area does not include a paper-out block or a damaged block, the CPU 31 determines whether a paper-out block or a damaged block is included in the target rectangular area adjacent to the target rectangular area on the downstream side in the forward direction. Determine whether or not. In this way, the CPU 31 continues conveying the paper P in the reverse direction and repeatedly executes the rectangular area processing until it detects the target rectangular area that includes the paperless block or the damaged block.

When the CPU 31 detects a target rectangular area that includes a paperless block or a damaged block (S16: YES), as shown in FIG. The starting position of the possible area is determined (S17). Further, the CPU 31 determines the return conveyance distance required to return the leading position to the position where printing can be performed by the print head 21 (S17).

After that, the CPU 31 issues a command to the motor M to drive the conveying rollers 16 and 17 in the rewinding direction, which is opposite to the feeding direction, so that the paper P is conveyed in the opposite direction (S18). After outputting this command, when the CPU 31 determines that the conveyance distance in the reverse direction of the paper P has reached the previously determined return conveyance distance (S19: YES), the CPU 31 sets a command so that the conveyance in the reverse direction of the paper P is stopped. A command is issued to the motor M to stop driving (S20), and the cue processing is completed.

On the other hand, if the CPU 31 determines that all blocks in the target rectangular area are not blocks with paper (S13: NO), the CPU 31 causes the motor M to move the transport rollers 16 and 17 in the feeding direction so that the paper P is transported in the forward direction. A driving command is issued (S21). When the paper P starts to be transported in the forward direction, the CPU 31 newly executes rectangular area processing (S22). Then, the CPU 31 determines whether all blocks included in the target rectangular area in the new rectangular target process are blocks with paper based on the result of the newly executed rectangular area process. If all blocks in the target rectangular area are not blocks with paper, the CPU 31 determines whether all blocks in the target rectangular area adjacent to the upstream side in the forward direction with respect to the target rectangular area are blocks with paper. . In this way, the CPU 31 continues transporting the paper P in the forward direction and repeatedly executes the rectangular area processing until it detects a target rectangular area in which all blocks are blocks with paper.

When the CPU 31 detects a target rectangular area in which all blocks are blocks with paper (S23: YES), as shown in FIG. The first position is determined (S17). Further, the CPU 31 determines the return conveyance distance required to return the leading position to the position where printing can be performed by the print head 21 (S17).

After that, the CPU 31 issues a command to the motor M to drive the conveying rollers 16 and 17 in the rewinding direction, which is opposite to the feeding direction, so that the paper P is conveyed in the opposite direction (S18). After outputting this command, when the CPU 31 determines that the conveyance distance in the reverse direction of the paper P has reached the previously determined return conveyance distance (S19: YES), the CPU 31 sets a command so that the conveyance in the reverse direction of the paper P is stopped. A command is issued to the motor M to stop driving (S20), and the cue processing is completed.

<Effect>
As described above, the paper P is read by the reading device 22, and the driving direction of the conveyance rollers 16 and 17 by the motor M is determined based on the image data obtained by the reading. Then, while the paper P is being transported in the transport direction corresponding to the determined driving direction, the paper P is read by the reading device 22, and the leading position of the usable area of the paper P is searched. Based on this search result, the print start position of the image by the print head 21 can be correctly set to the leading position of the usable area of the paper P, regardless of the surface condition of the paper P.

To search for the leading position, the reading device 22 reads an area of length A in the sub-scanning direction while the paper P is being conveyed in the forward direction. From the image data read by the reading device 22, edges on both sides of the paper P in the sub-scanning direction, which is the width direction, are detected. Thereafter, the image data included between the edges on both sides is divided into a predetermined number of blocks, and it is determined whether each block belongs to a block with paper, a block without paper, or a damaged block.

If all the blocks included in the target rectangular area between the edges are blocks with paper, the paper P is conveyed in the opposite direction, and the target rectangular area including the block without paper or the damaged block is searched. Then, when a target rectangular area including a paperless block or a damaged block is detected, the most upstream position in the forward direction in the target rectangular area is determined to be the leading position of the usable area on the paper P. On the other hand, if all the blocks included in the target rectangular area between the edges are not blocks with paper, that is, if the target rectangular area between the edges includes blocks without paper or damaged blocks, the paper P is transported in the forward direction. Then, a target rectangular area that does not include paperless blocks and damaged blocks, that is, a target rectangular area in which all blocks are paper blocks, is searched. Then, when a target rectangular area in which all blocks are sheets-containing blocks is detected, the most downstream position in the forward direction in the target rectangular area is determined to be the leading position of the usable area on the paper P. As a result, the usable area can be maximized without including parts unsuitable for printing, such as parts where the surface of the paper P has been torn off thinly, and the usable area can be secured to the maximum. This can prevent usable areas from being wasted.

<Modified example>
Although one embodiment of the present invention has been described above, the present invention can also be implemented in other forms.

For example, in the above embodiment, the edges on both sides of the paper P in the width direction are detected, and the division value obtained by dividing the number of image data included between these edges by a predetermined number is the length B of one block in the main scanning direction. It is assumed that the target rectangular area is divided into a predetermined number of blocks based on the length B. The present invention is not limited to this, and the edges on both sides of the paper P in the width direction are detected, and as shown in FIG. The target rectangular area may be divided into blocks of C (length C) and include all the divided blocks.

Furthermore, in the embodiment described above, the case where the CPU 31 executes each process in the label printer 1 has been described. However, the label printer 1 may be provided with a plurality of CPUs, and the plurality of CPUs may cooperate to execute each process.

In addition, various design changes can be made to the above-described configuration within the scope of the claims.

1: Label printer 16, 17: Conveyance roller 21: Print head 22: Reading device 31: CPU
M: Motor P: Paper

Claims (10)

A transport unit that transports long printing paper;
a drive unit that drives the transport unit;
a printing unit that prints an image on printing paper conveyed by the conveyance unit;
a reading section that can read the entire width of the printing paper in the width direction perpendicular to the conveying direction of the printing paper;
comprising a control unit;
The reading unit is disposed on the downstream side of the printing unit in the conveying direction of printing paper when printing by the printing unit,
The control unit includes:
a first driving process for instructing the driving unit to drive the transporting unit in the same sending direction as when printing by the printing unit;
a first reading process that issues a command to the reading unit to start reading after issuing a command by the first drive process, and causes the reading unit to read the printing paper;
Based on the image data read by the reading unit in the first reading process, the driving direction of the conveyance unit is determined to be the feeding direction or the rewinding direction opposite to the feeding direction, and the conveyance is carried out in the determined direction. a second driving process for issuing a command to the driving section to drive the section;
After issuing a command by the second drive process, a second reading process instructs the reading unit to start reading, and causes the reading unit to read the printing paper;
A rectangular area whose length in the transport direction is a predetermined distance and whose length in the width direction is a predetermined width is set based on the image data read by the reading unit in the second reading process. , a head search process of detecting the rectangular area whose entire area is the front surface of the printing paper, and searching and determining the head position of the usable area of the printing paper based on the detected rectangular area;
Based on the leading position determined in the leading search process, a transporting distance in the opposite direction, which is the transporting direction of the printing paper according to the rewinding direction, is determined, and the printing paper travels the determined transporting distance in the reverse direction. performing a third drive process of issuing a command to the drive unit to be transported to the
printer. The printer according to claim 1,
In the head search process, the control unit includes:
Each time the printing paper is conveyed by the predetermined distance by the second drive process, the rectangular area is set, and the image data of the rectangular area read by the reading unit is arranged in a row in the width direction. Blocking processing to divide into multiple blocks,
Block type determination processing for determining whether the block is a block with paper, a block without paper, or a damaged block, based on the values of pixels included in the block, for each block divided by the blocking process. and execute,
printer. The printer according to claim 2,
In the head search process, the control unit includes:
From the result of the block type determination process, find the rectangular area in which all the blocks are blocks with paper, and perform a forward direction that is the conveying direction of the printing paper according to the feeding direction with respect to the found rectangular area. Determining whether or not the rectangular area adjacent to the downstream side includes the no paper block or the damaged block, and determining that the adjacent rectangular area includes the no paper block or the damaged block. If so, the most upstream position in the forward direction of the adjacent rectangular area is determined as the leading position;
printer. The printer according to claim 2,
In the head search process, the control unit includes:
From the result of the block type determination process, find the rectangular area that includes the paperless block or the damaged block, and perform a forward direction that is the printing paper conveyance direction corresponding to the feeding direction with respect to the found rectangular area. It is determined whether all the blocks in the rectangular area adjacent to the upstream side are the blocks with paper, and if it is determined that all the blocks in the adjacent rectangular area are the blocks with paper, the adjacent The printer determines the most downstream position in the forward direction of the rectangular area to be the leading position. The printer according to any one of claims 2 to 4,
In the blocking process, the control unit includes:
The edges of the printing paper on both sides in the width direction are detected from the image data read by the reading unit, and the number of image data included between the detected edges on both sides is divided by a predetermined number. Determine the length in the width direction,
printer. The printer according to any one of claims 2 to 4,
In the blocking process, the control unit includes:
The length of the block in the width direction is a predetermined number of pixels;
printer. 7. The printer according to claim 6,
In the blocking process, the control unit includes:
detecting edges on both sides of the printing paper in the width direction from the image data read by the reading unit, and dividing into the blocks each having the predetermined number of pixels with one edge as a reference;
printer. The printer according to any one of claims 2 to 7,
In the block type determination process, the control unit includes:
For each block, the average value of the pixel values included in the block is calculated, and by comparing the average value with a predetermined threshold, it is determined whether the block is one of the blocks with paper, blocks without paper, and damaged blocks. Determine whether
printer. The printer according to any one of claims 2 to 8,
In the head search process, the control unit includes:
When it is determined that all the blocks in the rectangular area are the paper-containing blocks, if the difference between the average values of pixel values of each block is greater than a certain value, the maximum or minimum of the average value of pixel values of each block is determined. Change the judgment of a block to a damaged block,
printer. The printer according to any one of claims 1 to 9,
The control unit includes:
After determining the leading position in the leading search process, issuing a command to the drive unit to drive the transport unit in the rewinding direction, and moving the leading position to a position where printing can be performed by the printing unit;
printer.

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