JP6891463B2 - Image forming device and program - Google Patents

Description

The present invention relates to an image forming apparatus, contact and program.

The inkjet image forming apparatus repeatedly moves the carriage equipped with the recording head back and forth in the main scanning direction, ejects ink from the recording head, and conveys the recording medium in the sub-scanning direction using a conveying roller. There are many configurations that form. At this time, there is a problem that the transport amount (feed amount) of the recording medium fluctuates due to the variation in the diameter of the transport roller, the mounting state, the eccentricity, and the type of the recording medium. If the amount of ink transported fluctuates, the ink landing position may shift in the sub-scanning direction.

A transfer control device that reduces fluctuations in the transfer amount of such a recording medium is known (for example, Patent Document 1). In this transfer control device, the actual position information of the mark actually detected by the sensor when the transfer roller makes one rotation and the theoretical position information of the mark ideally detected by the sensor when the transfer roller makes one rotation. Calculate the difference. Then, based on the calculated difference, the corrected feed amount of each mark is calculated from the actual feed amount. Next, the error (error of the feed amount) between the corrected feed amount of each mark and the theoretical feed amount of each mark determined in advance is obtained in correspondence with the rotation position of the transport roller. Based on the relationship between the rotation position of the transfer roller and the obtained error (error of the feed amount), the correction amount for correcting the transfer amount of the recording medium by the transfer roller is calculated, and the calculated correction amount is used for the transfer roller. Is in control.

In order to appropriately adjust the image formation position according to the ink landing position shift due to the fluctuation of the transport amount of the recording medium, it is necessary to know the position shift amount. However, in the transfer control device of Patent Document 1, the correction amount for correcting the transfer amount of the transfer roller is calculated from the difference between the actual position information detected by the sensor and the theoretical position information that is ideally detected. However, the amount of misalignment cannot be calculated.

Even if the amount of misalignment in the captured image can be detected, it is necessary to know the ratio of the distance to the actual distance in the captured image in order to obtain the actual distance from the amount of misalignment in the captured image. Here, the ratio of the distance to the actual distance in the captured image changes as the distance between the two-dimensional sensor and the subject (recording medium) fluctuates, so that the distance between the two-dimensional sensor and the test pattern fluctuates. In the environment, the actual distance cannot be obtained from the amount of misalignment in the captured image.

The present invention has been made in view of the above, and even when the distance between the image pickup unit and the test pattern fluctuates, the position according to the amount of misalignment in the image captured by the image pickup unit. The purpose is to properly calculate the actual distance of the amount of deviation.

In order to solve the above-mentioned problems and achieve the object, the present invention has a transport control unit for transporting an object to be transported, an image forming unit for forming an image on the transported object, and the image forming unit. Is used to form either a first marker or a pair of second markers on the object to be transported, and after the object to be transported is transported in a predetermined transport amount, the first marker is not formed before transport. An image pickup unit that images a test pattern including the marker and the pair of second markers, a pattern forming unit that forms the marker and the pair of second markers, and an image pickup image that is imaged by the image pickup unit. The distance between the position detection unit that detects the positions of the first marker and the pair of second markers in the image, the pair of second markers in the captured image, and the positional deviation of the first markers in the captured image. The ratio calculation unit that calculates the ratio to the amount and the actual distance between the pair of second markers are multiplied by the ratio to calculate the actual distance of the displacement amount of the first marker with respect to the pair of second markers. It is provided with an actual distance calculation unit.

According to the present invention, even when the distance between the image pickup unit and the test pattern fluctuates, the actual distance of the position shift amount according to the position shift amount in the captured image captured by the image pickup unit is appropriately calculated. It has the effect of being able to do it.

FIG. 1 is a perspective view showing the inside of the image forming apparatus of the first embodiment as a perspective view. FIG. 2 is a top view showing the internal mechanical configuration of the image forming apparatus of the first embodiment. FIG. 3 is an explanatory view of the carriage. FIG. 4 is a perspective view showing the appearance of the imaging unit. FIG. 5 is an exploded perspective view of the imaging unit. FIG. 6 is a vertical cross-sectional view of the imaging unit as viewed from the X1 direction in FIG. FIG. 7 is a vertical cross-sectional view of the imaging unit as viewed from the X2 direction in FIG. FIG. 8 is a plan view of the imaging unit. FIG. 9 is a diagram showing a specific example of the reference chart. FIG. 10 is a vertical cross-sectional view of the imaging unit. FIG. 11 is a plan view of the imaging unit of FIG. 10 as viewed from the X2 direction. FIG. 12 is a configuration diagram around the transport roller. FIG. 13 is a hardware configuration diagram of the image forming apparatus of the first embodiment. FIG. 14 is a block diagram showing a functional configuration of the image forming apparatus of the first embodiment. FIG. 15 is a diagram showing an example of a test pattern formed on a recording medium. FIG. 16 is an explanatory diagram of a method of forming a test pattern. FIG. 17 is an explanatory diagram of a method of calculating the ratio of the distance between the pair of second markers M2a and M2b in the captured image and the amount of misalignment of the first marker M1. FIG. 18 is a diagram illustrating an example in which a relative positional deviation occurs between the first marker M1 included in the test pattern and the pair of second markers M2a and M2b. FIG. 19 is a diagram for explaining the amount of misalignment of the first marker M1 with respect to the pair of second markers M2a and M2b. FIG. 20 is a diagram for explaining the amount of misalignment of the first marker M1 with respect to the pair of second markers M2a and M2b when the distance between the imaging unit and the test pattern fluctuates. FIG. 21 is a flowchart showing a flow of operations related to adjustment of a transport amount in the image forming apparatus of the first embodiment. FIG. 22 is a diagram showing an example of a test pattern formed by linear markers. FIG. 23 is a diagram showing an example of a test pattern formed by a plurality of linear markers. FIG. 24 is a diagram showing an example of a test pattern and a reference frame formed by a plurality of linear markers. FIG. 25 is a flowchart showing the flow of operations related to the adjustment of the transport amount in the image forming apparatus of the modified example of the first embodiment. FIG. 26 is a hardware configuration diagram of the image forming apparatus of the second embodiment. FIG. 27 is a block diagram showing a functional configuration of the image forming apparatus of the second embodiment.

The image forming apparatus, the distance calculation method, and the embodiment of the program will be described in detail with reference to the accompanying drawings. In the embodiment described below, as an example of the image forming apparatus, an inkjet printer that ejects ink to a recording medium, which is an example of an object to be transported, to form an image will be illustrated. This image forming apparatus captures a test pattern formed on a recording medium, calculates a distance corresponding to the amount of misalignment when the ink landing position is misaligned using the captured image, and conveys the amount of the recording medium. It has a function to adjust the parameters related to. However, application examples of the present invention are not limited to the embodiments described below. The present invention can be widely applied to various types of image forming apparatus that image a test pattern and calculate a distance corresponding to the amount of misalignment using the captured image.

(First Embodiment)
<Mechanical configuration of image forming apparatus>
First, a mechanical configuration example of the image forming apparatus 100 of the present embodiment will be described with reference to the drawings. FIG. 1 is a perspective view showing the inside of the image forming apparatus of the first embodiment as a perspective view. FIG. 2 is a top view showing the internal mechanical configuration of the image forming apparatus of the first embodiment. FIG. 3 is an explanatory view of the carriage.

As shown in FIG. 1, the image forming apparatus 100 of the present embodiment includes a carriage 5 that reciprocates in the main scanning direction (direction of arrow A in the drawing). The carriage 5 is supported by a main guide rod 3 extending along the main scanning direction. Further, the carriage 5 is provided with a connecting piece 5a. The connecting piece 5a engages with the sub-guide member 4 provided in parallel with the main guide rod 3 to stabilize the posture of the carriage 5.

The carriage 5 is connected to a timing belt 11 stretched between the drive pulley 9 and the driven pulley 10. The drive pulley 9 is rotated by driving the main scanning motor 8. The driven pulley 10 has a mechanism for adjusting the distance between the driven pulley 10 and the drive pulley 9, and has a role of applying a predetermined tension to the timing belt 11. The carriage 5 reciprocates in the main scanning direction by the timing belt 11 being fed by driving the main scanning motor 8. As shown in FIG. 2, for example, the movement amount and the movement speed of the carriage 5 are controlled based on the encoder value that the main scanning encoder sensor 131 provided on the carriage 5 detects and outputs the mark on the encoder sheet 14.

As shown in FIG. 3, the carriage 5 is equipped with recording heads 6A, 6B, and 6C. The recording head 6A has a nozzle row 6Ay in which a large number of nozzles for ejecting yellow (Y) ink are arranged, a nozzle row 6Ac in which a large number of nozzles for ejecting cyan (C) ink are arranged, and a large number for ejecting magenta (M) ink. Nozzle row 6Am in which the nozzles of Nozzle are arranged, and nozzle row 6Ak in which a large number of nozzles for ejecting black (K) ink are arranged are arranged one by one. Similarly, the recording head 6B has nozzle rows 6By, 6Bc, 6Bm, 6Bk, and the recording head 6C has nozzle rows 6Cy, 6Cc, 6Cm, 6Ck. Hereinafter, these recording heads 6A, 6B, and 6C are collectively referred to as a recording head 6. The recording head 6 is supported by the carriage 5 so that its discharge surface (nozzle surface) faces downward (recording medium P side).

The cartridge 7, which is an ink supply body for supplying ink to the recording head 6, is not mounted on the carriage 5, but is arranged at a predetermined position in the image forming apparatus 100. The cartridge 7 and the recording head 6 are connected by a pipe, and ink is supplied from the cartridge 7 to the recording head 6 through the pipe.

As shown in FIG. 2, a platen 16 is provided at a position facing the discharge surface of the recording head 6. The platen 16 is for supporting the recording medium P when the ink is ejected from the recording head 6 onto the recording medium P. The platen 16 is provided with a large number of through holes penetrating in the thickness direction, and rib-shaped protrusions are formed so as to surround the individual through holes. Then, by operating the suction fan provided on the side of the platen 16 opposite to the surface supporting the recording medium P, the recording medium P is prevented from falling off from the platen 16. The recording medium P is sandwiched by a transfer roller driven by a sub-scanning motor 12 (see FIG. 13) described later, and is intermittently conveyed on the platen 16 in the sub-scanning direction (arrow B direction in the drawing).

As described above, the recording head 6 is provided with a large number of nozzles formed so as to line up in the sub-scanning direction. The image forming apparatus 100 of the present embodiment intermittently conveys the recording medium P in the sub-scanning direction, and while the conveying of the recording medium P is stopped, moves the carriage 5 back and forth in the main scanning direction while moving the image. The nozzle of the recording head 6 is selectively driven according to the data, ink is ejected from the recording head 6 onto the recording medium P on the platen 16, and an image is recorded on the recording medium P.

Further, the image forming apparatus 100 of the present embodiment includes a maintenance mechanism 15 for maintaining the reliability of the recording head 6. The maintenance mechanism 15 cleans and caps the ejection surface of the recording head 6, ejects unnecessary ink from the recording head 6, and the like.

Further, as shown in FIG. 3, the carriage 5 is equipped with an imaging unit 20 for imaging a test pattern TP (see FIG. 15) formed on the recording medium P, which will be described later. Details of the imaging unit 20 will be described later.

Each of the above-mentioned components constituting the image forming apparatus 100 of the present embodiment is arranged inside the exterior body 1. A cover member 2 is provided on the exterior body 1 so as to be openable and closable. By opening the cover member 2 during maintenance of the image forming apparatus 100 or when a jam occurs, it is possible to perform work on each component provided inside the exterior body 1.

The imaging unit 20 shown in FIG. 3 may or may not have a reference chart that is imaged at the same time as the test pattern TP. The reference chart is for calculating the color measurement value of the test pattern TP using, for example, the RGB values of each reference patch (see FIG. 9).

<Specific example 1 of the imaging unit>
First, a specific example of the imaging unit 20 having a reference chart will be described. FIG. 4 is a perspective view showing the appearance of the imaging unit. FIG. 5 is an exploded perspective view of the imaging unit. FIG. 6 is a vertical cross-sectional view of the imaging unit as viewed from the X1 direction in FIG. FIG. 7 is a vertical cross-sectional view of the imaging unit as viewed from the X2 direction in FIG. FIG. 8 is a plan view of the imaging unit.

The imaging unit 20 includes, for example, a housing 51 formed in a rectangular box shape. The housing 51 has, for example, bottom plate portions 51a and top plate portions 51b facing each other at predetermined intervals, and side wall portions 51c, 51d, 51e, 51f connecting these bottom plate portions 51a and the top plate portion 51b. The bottom plate portion 51a and the side wall portions 51d, 51e, 51f of the housing 51 are integrally formed by, for example, molding, whereas the top plate portion 51b and the side wall portion 51c are detachable. FIG. 5 shows a state in which the top plate portion 51b and the side wall portion 51c are removed.

The imaging unit 20 is installed in the transport path of the recording medium P on which the test pattern TP is formed, for example, with a part of the housing 51 supported by a predetermined support member. At this time, as shown in FIGS. 6 and 7, the imaging unit 20 faces the conveyed recording medium P so that the bottom plate portion 51a of the housing 51 faces the conveyed recording medium P in a substantially parallel state through the gap d. It is supported by a predetermined support member.

The bottom plate portion 51a of the housing 51 facing the recording medium P on which the test pattern TP is formed is provided with an opening 53 for allowing the test pattern TP outside the housing 51 to be imaged from the inside of the housing 51. Has been done.

Further, a reference chart 300 is arranged on the inner surface side of the bottom plate portion 51a of the housing 51 so as to be adjacent to the opening 53 via the support member 63. The reference chart 300 is imaged together with the test pattern TP by the sensor unit 26 described later when measuring the color of the test pattern TP and acquiring the RGB value. The details of the reference chart 300 will be described later.

On the other hand, the circuit board 54 is arranged on the top plate portion 51b side inside the housing 51. As shown in FIG. 8, a square box-shaped housing 51 having an open surface on the circuit board 54 side is fixed to the circuit board 54 by a fastening member 54b. The housing 51 is not limited to a square box shape, and may be, for example, a cylindrical box shape having a bottom plate portion 51a in which the opening 53 is formed, an elliptical box shape, or the like.

Further, a sensor unit 26 for capturing an image is arranged between the top plate portion 51b of the housing 51 and the circuit board 54. As shown in FIG. 6, the sensor unit 26 is a two-dimensional sensor 27 such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor, and the optical image of the imaging range of the sensor unit 26 is a two-dimensional sensor 27. An imaging lens 28 that forms an image on the light receiving surface (imaging region) of the The two-dimensional sensor 27 is a light receiving element array in which light receiving elements that receive the reflected light from the subject are arranged in two dimensions.

The sensor portion 26 is held by, for example, a sensor holder 56 integrally formed with the side wall portion 51e of the housing 51. The sensor holder 56 is provided with a ring portion 56a at a position facing the through hole 54a formed in the circuit board 54. The ring portion 56a has a through hole having a size that conforms to the outer shape of the protruding portion of the sensor portion 26 on the imaging lens 28 side. The sensor unit 26 inserts the protruding portion on the imaging lens 28 side into the ring portion 56a of the sensor holder 56, so that the imaging lens 28 passes through the through hole 54a of the circuit board 54 and the bottom plate portion 51a of the housing 51. It is held by the sensor holder 56 so as to face the side.

At this time, in the sensor unit 26, the optical axis indicated by the alternate long and short dash line in FIG. 6 is substantially perpendicular to the bottom plate portion 51a of the housing 51, and the opening 53 and the reference chart 300 described later are included in the imaging range. It is held in a positioned state by the sensor holder 56 so as to be. As a result, the sensor unit 26 images the test pattern TP outside the housing 51 through the opening 53 in a part of the imaging region of the two-dimensional sensor 27. In addition, the sensor unit 26 can image the reference chart 300 arranged inside the housing 51 in another part of the imaging region of the two-dimensional sensor 27.

The sensor unit 26 is electrically connected to the circuit board 54 on which various electronic components are mounted, for example, via a flexible cable. Further, the circuit board 54 is provided with an external connection connector 57 to which a connection cable for connecting the image pickup unit 20 to the main control board of the image forming apparatus 100 is mounted.

The imaging unit 20 is on a circuit board 54 located on the center line OA in the sub-scanning direction passing through the center of the sensor unit 26 and at positions separated from the center of the sensor unit 26 in the sub-scanning direction by a predetermined amount at equal intervals. , A pair of light sources 58 are arranged. The light source 58 illuminates the imaging range substantially uniformly at the time of imaging by the sensor unit 26. As the light source 58, for example, an LED (Light Emitting Diode) which is advantageous for space saving / power saving is used.

In the present embodiment, as shown in FIGS. 7 and 8, a pair of LEDs are evenly arranged in a direction orthogonal to the direction in which the opening 53 and the reference chart 300 are arranged with the center of the imaging lens 28 as a reference. It is used as a light source 58.

The two LEDs used as the light source 58 are mounted on, for example, the surface of the circuit board 54 on the bottom plate portion 51a side. However, the light source 58 may be arranged at a position where the imaging range of the sensor unit 26 can be illuminated substantially uniformly by diffused light, and may not necessarily be directly mounted on the circuit board 54. Further, the positions of the two LEDs are arranged symmetrically with respect to the two-dimensional sensor 27, so that the imaging surface can be imaged under the same illumination conditions as the reference chart 300 side. Further, in the present embodiment, the LED is used as the light source 58, but the type of the light source 58 is not limited to the LED. For example, an organic EL or the like may be used as the light source 58. When the organic EL is used as the light source 58, the illumination light close to the spectral distribution of sunlight can be obtained, so that the color measurement accuracy can be expected to be improved.

Further, as shown in FIG. 8, the sensor unit 26 includes a light absorber 55c directly below the light source 58 and the two-dimensional sensor 27. The light absorber 55c reflects or absorbs the light from the light source 58 in a direction other than the two-dimensional sensor 27. The light absorber 55c has an acute-angled shape, and is formed so that the incident light from the light source 58 is reflected to the inner surface of the light absorber 55c, and has a structure that does not reflect in the incident direction.

Further, inside the housing 51, an optical path length changing member 59 is provided in the optical path between the sensor unit 26 and the test pattern TP outside the housing 51 imaged through the opening 53 by the sensor unit 26. Have been placed. The optical path length changing member 59 is an optical element having a refractive index n having sufficient transmittance for the light of the light source 58. The optical path length changing member 59 has a function of bringing the image plane of the optical image of the test pattern TP outside the housing 51 closer to the image plane of the optical image of the reference chart 300 inside the housing 51. That is, in the imaging unit 20, the optical path length is changed by arranging the optical path length changing member 59 in the optical path between the sensor unit 26 and the subject outside the housing 51. As a result, the image pickup unit 20 has both the image plane of the optical image of the test pattern TP outside the housing 51 and the image plane of the reference chart 300 inside the housing 51 of the two-dimensional sensor 27 of the sensor unit 26. It is designed to match the light receiving surface. Therefore, the sensor unit 26 can capture an image in which both the test pattern TP outside the housing 51 and the reference chart 300 inside the housing 51 are in focus.

As shown in FIG. 6, for example, in the optical path length changing member 59, both ends of the surface on the bottom plate portion 51a side are supported by a pair of ribs 60 and 61. Further, by arranging the pressing member 62 between the surface of the optical path length changing member 59 on the top plate portion 51b side and the circuit board 54, the optical path length changing member 59 does not move inside the housing 51. There is. The optical path length changing member 59 is arranged so as to close the opening 53 provided in the bottom plate portion 51a of the housing 51. Therefore, in the optical path length changing member 59, impurities such as ink mist and dust that enter the inside of the housing 51 from the outside of the housing 51 through the opening 53 adhere to the sensor unit 26, the light source 58, the reference chart 300, and the like. It will also have a function to prevent.

The mechanical configuration of the imaging unit 20 described above is merely an example, and is not limited to this. At least while the light source 58 provided inside the housing 51 is lit, the imaging unit 20 uses the sensor unit 26 provided inside the housing 51 to open the test pattern TP outside the housing 51 through the opening 53. Any configuration may be used as long as the image is taken through the image. The imaging unit 20 can be variously modified or changed with respect to the above configuration.

For example, in the image pickup unit 20 described above, the reference chart 300 is arranged on the inner surface side of the bottom plate portion 51a of the housing 51. However, an opening different from the opening 53 is provided at a position where the reference chart 300 of the bottom plate portion 51a of the housing 51 is arranged, and the reference chart 300 is provided from the outside of the housing 51 at the position where the opening is provided. It may be configured to attach. In this case, the sensor unit 26 captures the test pattern TP formed on the recording medium P through the opening 53, and at the same time, the sensor unit 26 reaches the bottom plate portion 51a of the housing 51 via an opening different from the opening 53. The reference chart 300 attached from the outside will be imaged. In this example, there is an advantage that the reference chart 300 can be easily replaced when a defect such as dirt occurs.

Next, a specific example of the reference chart 300 arranged in the housing 51 of the imaging unit 20 will be described with reference to FIG. FIG. 9 is a diagram showing a specific example of the reference chart.

The reference chart 300 shown in FIG. 9 has a plurality of color measurement patch rows 310 to 340 in which color measurement patches for color measurement are arranged, a distance measurement line 350, and a chart position identification marker 360.

The color measurement patch rows 310 to 340 are a color measurement patch row 310 in which YMCK primary color measurement patches are arranged in gradation order, and a color measurement patch row in which RGB secondary color measurement patches are arranged in gradation order. Includes 320, a color measurement patch sequence (achromatic gradation pattern) 330 in which gray scale color measurement patches are arranged in gradation order, and a color measurement patch sequence 340 in which tertiary color measurement patches are arranged.

The distance measurement line 350 is formed as a rectangular frame surrounding a plurality of colorimetric patch rows 310 to 340. The chart position specifying marker 360 is provided at the four corners of the distance measurement line 350, and functions as a marker for specifying the position of each color measurement patch. The position of the reference chart 300 and the position of each color measurement patch are specified by specifying the distance measurement line 350 and the chart position identification markers 360 at the four corners thereof from the image of the reference chart 300 captured by the sensor unit 26. be able to.

Each color measurement patch constituting the color measurement patch rows 310 to 340 for color measurement is used as a reference for color tones reflecting the imaging conditions of the sensor unit 26. The configuration of the color measurement patch rows 310 to 340 arranged on the reference chart 300 is not limited to the example shown in FIG. 9, and any color measurement patch row can be applied. Is. For example, a color measurement patch that can specify a color range as wide as possible may be used, and the YMCK primary color measurement patch row 310 and the grayscale color measurement patch row 330 may be used in the image forming apparatus 100. It may be composed of a patch of color measurement values of the color material used for. Further, the RGB secondary color measurement patch row 320 may be composed of patches of color measurement values capable of developing colors with the color material used in the image forming apparatus 100, and further, color measurement such as Japan Color. A reference color chart with a defined value may be used.

In the present embodiment, the reference chart 300 having the color measurement patch rows 310 to 340 in the shape of a general patch (color tag) is used, but the reference chart 300 does not necessarily have such a color measurement patch row 310. It does not have to be in the form of ~ 340. The reference chart 300 may have a configuration in which a plurality of colors that can be used for color measurement are arranged so that their respective positions can be specified.

As described above, since the reference chart 300 is arranged on the inner surface side of the bottom plate portion 51a of the housing 51 so as to be adjacent to the opening 53, the sensor portion 26 simultaneously performs the test pattern TP outside the housing 51. It can be imaged. Note that simultaneous imaging here means acquiring one frame of image data including the test pattern TP outside the housing 51 and the reference chart 300. That is, even if there is a time lag in data acquisition for each pixel, if the image data in which the test pattern TP outside the housing 51 and the reference chart 300 are included in one frame is acquired, the test pattern TP outside the housing 51 can be obtained. This means that the reference chart 300 and the reference chart 300 are imaged at the same time.

<Specific example 2 of the imaging unit>
Next, a specific example of the imaging unit 20 that does not have a reference chart will be described. Hereinafter, a specific example of the imaging unit 20 will be described in detail with reference to FIGS. 10 and 11. FIG. 10 is a vertical cross-sectional view of the imaging unit. FIG. 11 is a plan view of the imaging unit of FIG. 10 as viewed from the X2 direction.

As shown in FIG. 10, the image pickup unit 20 has a light source 42 and a sensor unit 26 mounted on a substrate 41 fixed to the carriage 5.

As the light source 42, for example, an LED is used, and the test pattern TP formed on the recording medium P, which is the subject, is irradiated with illumination light, and the reflected light (diffusely reflected light or specularly reflected light) is the sensor unit 26. Is incident on. As shown in FIG. 11, four light sources 42 are arranged so as to surround the test pattern TP formed on the recording medium P, and irradiate the test pattern TP with uniform illumination light.

The sensor unit 26 includes a two-dimensional sensor 27 such as a CCD sensor or a CMOS sensor, and an imaging lens 28. The sensor unit 26 causes the reflected light of the illumination light emitted from the light source 42 to the test pattern TP to enter the two-dimensional sensor 27 through the imaging lens 28. The two-dimensional sensor 27 converts the incident light into an analog signal by photoelectric conversion, and outputs it as an captured image of the test pattern TP.

<Details of the transport section>
Next, a transport unit that transports the recording medium P, which is the object to be transported, will be described. FIG. 12 is a configuration diagram around the transport roller. As shown in FIG. 12, the recording medium P is intermittently conveyed in the sub-scanning direction (arrow B direction in the figure) orthogonal to the main scanning direction (arrow A direction in the figure) which is the moving direction of the carriage 5. At this time, the encoder 35 provided coaxially with the transport roller 152 is read by the sub-scanning encoder sensor 132 provided on the side plate (not shown).

The amount of the recording medium P conveyed is controlled by the sensor control unit 124 (see FIG. 13) electrically connected to the sub-scanning encoder sensor 132 based on the information read in this way. In this example, the encoder 35 is configured as a rotary encoder, and the optical grid is arranged in a disk shape so that an angle, a rotation amount, a rotation speed, and the like can be detected.

<Hardware configuration of image forming device>
Next, the hardware configuration of the image forming apparatus 100 of the present embodiment will be described with reference to FIG. FIG. 13 is a hardware configuration diagram of the image forming apparatus of the first embodiment.

As shown in FIG. 13, the image forming apparatus 100 of the present embodiment includes a CPU 110, a ROM 102, a RAM 103, a recording head driver 104, a main scanning driver 105, a sub scanning driver 106, a control FPGA (Field-Programmable Gate Array) 120, and the like. It includes a recording head 6, a main scanning encoder sensor 131, an image pickup unit 20, a main scanning motor 8, a transport unit 150, and a sub-scanning motor 12.

The CPU 110, ROM 102, RAM 103, recording head driver 104, main scanning driver 105, sub-scanning driver 106, and control FPGA 120 are mounted on the main control board 130. Further, the recording head 6, the main scanning encoder sensor 131, and the imaging unit 20 are mounted on the carriage 5 as described above. Further, the sub-scanning encoder sensor 132 and the transfer roller 152 are mounted on the transfer unit 150 described above.

The CPU 110 controls the entire image forming apparatus 100. For example, the CPU 110 uses the RAM 103 as a work area to execute various control programs stored in the ROM 102, and outputs control commands for controlling various operations in the image forming apparatus 100. In particular, in the image forming apparatus 100 of the present embodiment, the CPU 110 provides a function of forming a test pattern TP, a function of a distance measuring apparatus, a function of adjusting parameters related to the amount of transport of the recording medium P based on the distance, and the like. Realize. The details of these functions will be described later.

The recording head driver 104, the main scanning driver 105, and the sub-scanning driver 106 are drivers for driving the recording head 6, the main scanning motor 8, and the sub-scanning motor 12, respectively.

The control FPGA 120 controls various operations in the image forming apparatus 100 in cooperation with the CPU 110. The control FPGA 120 includes, for example, a CPU control unit 121, a memory control unit 122, an ink ejection control unit 123, a sensor control unit 124, and a motor control unit 125 as functional components.

The CPU control unit 121 communicates with the CPU 110, transmits various information acquired by the control FPGA 120 to the CPU 110, and inputs a control command output from the CPU 110.

The memory control unit 122 performs memory control for the CPU 110 to access the ROM 102 and the RAM 103.

The ink ejection control unit 123 controls the operation of the recording head driver 104 in response to a control command from the CPU 110 to control the ink ejection timing from the recording head 6 driven by the recording head driver 104.

The sensor control unit 124 processes sensor signals such as encoder values output from the main scanning encoder sensor 131 and the sub-scanning encoder sensor 132. For example, the sensor control unit 124 executes a process of calculating the position, moving speed, moving direction, and the like of the carriage 5 based on the encoder value output from the main scanning encoder sensor 131. Further, for example, the sensor control unit 124 executes a process of calculating the rotation speed, rotation direction, and the like of the transfer roller 152 that conveys the recording medium P based on the encoder value output from the sub-scanning encoder sensor 132.

The motor control unit 125 controls the operation of the main scanning driver 105 in response to a control command from the CPU 110 to control the main scanning motor 8 driven by the main scanning driver 105 in the main scanning direction of the carriage 5. Control the movement of. Further, the motor control unit 125 controls the operation of the sub-scanning driver 106 in response to a control command from the CPU 110 to control the sub-scanning motor 12 driven by the sub-scanning driver 106, and records by the transfer roller 152. The movement (conveyance) of the medium P in the sub-scanning direction is controlled.

It should be noted that each of the above parts is an example of the control function realized by the control FPGA 120, and various control functions other than these may be realized by the control FPGA 120. Further, all or a part of the above control functions may be realized by a program executed by the CPU 110 or another general-purpose CPU. Further, a part of the above control functions may be realized by dedicated hardware such as another FPGA or ASIC (Application Specific Integrated Circuit) different from the control FPGA 120.

The recording head 6 has a plurality of nozzles for ejecting ink to form an image (see FIG. 3), is driven by a recording head driver 104 whose operation is controlled by a CPU 110 and a control FPGA 120, and is a recording medium on a platen 16. Ink is ejected to P to form an image.

The main scanning encoder sensor 131 outputs the encoder value obtained by detecting the mark on the encoder sheet 14 to the control FPGA 120. This encoder value is used in the sensor control unit 124 of the control FPGA 120 to calculate the position, moving speed, and moving direction of the carriage 5. The position, moving speed, and moving direction of the carriage 5 calculated by the sensor control unit 124 from the encoder value are sent to the CPU 110. The CPU 110 generates a control command for controlling the main scanning motor 8 based on the position, the moving speed, and the moving direction of the carriage 5, and outputs the control command to the motor control unit 125.

The image pickup unit 20 takes an image of the test pattern TP formed on the recording medium P under the control of the CPU 110, and performs various processing on the captured image, and is a two-dimensional sensor CPU 140 and a two-dimensional image. It includes a sensor 27.

As described above, the two-dimensional sensor 27 is a CCD sensor, a CMOS sensor, or the like, and images the test pattern TP and the reference frame F under predetermined operating conditions based on various setting signals sent from the two-dimensional sensor CPU 140. To do. Then, the two-dimensional sensor 27 sends the captured image to the CPU 140 for the two-dimensional sensor.

The two-dimensional sensor CPU 140 controls the two-dimensional sensor 27 and processes the captured image captured by the two-dimensional sensor 27. Specifically, the two-dimensional sensor CPU 140 sets various operating conditions of the two-dimensional sensor 27 by sending various setting signals to the imaging unit 20. Further, the CPU 140 for a two-dimensional sensor realizes a function of detecting a marker of the test pattern TP from the captured image obtained by capturing the test pattern TP and a function of calculating the ratio of the distance to the actual distance in the captured image. The details of these functions will be described later.

Further, the image pickup unit 20 is provided with a RAM and a ROM, and the two-dimensional sensor CPU 140 uses, for example, the RAM as a work area to execute various control programs stored in the ROM, and the image pickup unit 20 has the image pickup unit 20. Outputs control commands for controlling various operations. Further, the CPU 140 for a two-dimensional sensor AD-converts an analog signal obtained by photoelectric conversion of the two-dimensional sensor 27 into digital image data, and shading correction, white balance correction, γ correction, and image data for the image data. It has a built-in function to perform various image processing such as format conversion. In addition, various image processing for the captured image may be configured so that a part or all of the image processing is performed outside the imaging unit 20.

The sub-scanning encoder sensor 132 outputs the encoder value obtained by reading the encoder 35 to the control FPGA 120. This encoder value is used in the sensor control unit 124 of the control FPGA 120 to calculate the rotation speed and the rotation direction of the transfer roller 152 that conveys the recording medium P. The rotation speed and rotation direction of the transfer roller 152 calculated by the sensor control unit 124 from the encoder value are sent to the CPU 110. The CPU 110 generates a control command for controlling the sub-scanning motor 12 based on the rotation speed and the rotation direction of the transfer roller 152, and outputs the control command to the motor control unit 125.

The transport roller 152 transports the recording medium P at a predetermined transport amount by rotating at a rotation speed and a rotation direction based on a control command received from the motor control unit 125.

In the image forming apparatus 100 of the present embodiment, the recording head driver 104, the main scanning driver 105, and the sub-scanning driver 106 controlled by the CPU 110 and the control FPGA 120 described above, the recording head 6 driven by these, and the main scanning motor 8 are used. The sub-scanning motor 12 and the sub-scanning motor 12 constitute an image forming unit that forms an image on the recording medium P.

In FIG. 13, the two-dimensional sensor CPU 140 and the imaging unit 20 are mounted on the carriage 5, but the two-dimensional sensor CPU 140 and the imaging unit 20 have a test pattern TP formed on the recording medium P. It does not have to be mounted on the carriage 5 as long as it is arranged so that it can be appropriately imaged.

<Functional configuration of image forming device>
Next, with reference to FIG. 14, characteristic functions realized by the CPU 110 of the image forming apparatus 100 and the CPU 140 for a two-dimensional sensor will be described. FIG. 14 is a block diagram showing a functional configuration of the image forming apparatus of the first embodiment.

The CPU 110 uses, for example, the RAM 103 as a work area to execute a control program stored in the ROM 102 to perform functions such as a pattern forming unit 111, an actual distance calculation unit 114, an adjusting unit 115, and a transport control unit 116. To realize. Further, the two-dimensional sensor CPU 140 of the imaging unit 20 can function as a position detection unit 142 and a ratio calculation unit 143 by implementing a control program stored in the ROM by using, for example, a RAM as a work area. Realize.

The transport control unit 116 of the CPU 110 controls the transport roller 152 of the transport unit 150 that transports the recording medium P. For example, the transfer control unit 116 determines the rotation speed and rotation direction of the transfer roller 152 based on the encoder value output from the sub-scanning encoder sensor 132, and controls a control command indicating the rotation speed and rotation direction. The transfer of the recording medium P by the transfer roller 152 is controlled by sending it to the transfer roller 152 of the transfer unit 150 via the FPGA 120.

The pattern forming unit 111 of the CPU 110 reads the pattern data stored in advance in, for example, the ROM 102 or the like, and causes the above-mentioned image forming unit to perform an image forming operation according to the pattern data, whereby the test pattern TP is performed on the recording medium P. To form. The test pattern TP formed on the recording medium P by the pattern forming unit 111 is imaged by the imaging unit 20.

The test pattern TP of the present embodiment is a set M of markers including at least the first marker M1 and a pair of second markers M2a and M2b. The details of the test pattern TP will be described later (see FIG. 15). The pattern forming unit 111 formed either one of the first marker M1 and the pair of second markers M2a and M2b on the recording medium P by using the image forming unit, and the recording medium P was conveyed by a predetermined conveying amount. After that, either one of the first marker M1 and the pair of second markers M2a and M2b that are not formed before the transfer is formed.

In the present embodiment, the pattern forming unit 111 forms an example in which the first marker M1 is formed on the recording medium P, and the pair of second markers M2a and M2b are formed after the recording medium P is conveyed by a predetermined transfer amount. I will explain. As described above, the order may be either, and the pattern forming unit 111 forms a pair of second markers M2a and M2b on the recording medium P, and the first marker is conveyed after the recording medium P is conveyed by a predetermined conveying amount. M1 may be formed.

Here, the test pattern TP will be described. FIG. 15 is a diagram showing an example of a test pattern formed on a recording medium. As shown in FIG. 15, the test pattern TP is a set M of markers including at least the first marker M1 and a pair of second markers M2a and M2b. In the test pattern TP shown in FIG. 15, the first marker M1 is arranged between the pair of second markers M2a and M2b. Further, the first marker M1 and the pair of second markers M2a and M2b are formed by dots and are formed along the sub-scanning direction (arrow B direction in the drawing) which is the transport direction of the recording medium P.

Next, a method of forming a test pattern will be described. FIG. 16 is an explanatory diagram of a method of forming a test pattern. First, as shown in FIG. 16A, the pattern forming unit 111 forms the first marker M1 on the recording medium P. Next, as shown in FIG. 16B, the transfer control unit 116 uses the transfer roller 152 to transfer the recording medium P to a predetermined transfer amount L1 (actual transfer amount L1) in the sub-scanning direction (arrow B direction in the drawing). Transport. Then, as shown in FIG. 16C, the pattern forming unit 111 forms the second markers M2a and M2b after the actual transfer amount L1 is transferred. The pair of second markers M2a and M2b are two nozzles (designated) separated by a distance e on both front and rear sides in the sub-scanning direction with reference to a nozzle separated by an ideal transfer amount L2 from the nozzle forming the first marker M1. It is formed by a nozzle). In the following, the reference nozzle may be referred to as a reference nozzle, and two nozzles separated from the reference nozzle by a distance e in the front-rear direction in the sub-scanning direction may be referred to as a designated nozzle.

Therefore, when the actual transport amount L1 actually transported and the ideal transport amount L2 are the same, the first marker M1 is formed at an ideal position which is an intermediate position in the sub-scanning direction of the pair of second markers M2a and M2b. A test pattern TP is formed. On the other hand, if the actual transport amount L1 and the ideal transport amount L2 are different, for example, the first marker M1 is formed at a position close to either marker even between the pair of second markers M2a and M2b. A test pattern TP is formed.

Then, by photographing this test pattern TP and calculating the relative positional relationship between the first marker M1 and the pair of second markers M2a and M2b, the amount of deviation between the ideal transport amount L2 and the actual transport amount L1 can be determined. I will ask. In the present embodiment, an example in which the ideal position of the first marker M1 is an intermediate position between the pair of second markers M2a and M2b will be described, but it does not have to be an intermediate position between the pair of second markers M2a and M2b. .. That is, if the first marker M1 can be imaged together with the pair of second markers M2a and M2b and is formed at a predetermined position, the ideal position of the first marker M1 is the pair of second markers M2a. , M2b may be close to either one, or may not be between the pair of second markers M2a and M2b.

Further, the pattern forming unit 111 may form the first marker M1 and the pair of second markers M2a and M2b with nozzles in the same row, or may be formed at positions separated by a distance e from the reference nozzle in the sub-scanning direction. If possible, it may be formed with different rows of nozzles. That is, the pair of second markers M2a and M2b may be displaced in the main scanning direction.

Specifically, as described above, each recording head 6 of the present embodiment is formed with four rows of nozzles of each color in which a large number of nozzles are lined up in the sub-scanning direction (see FIG. 3). For example, the pattern forming unit 111 ejects ink from nozzles in the same row among the four rows (plurality) of nozzle rows of the recording head 6A to form a first marker M1 and a pair of second markers M2a and M2b. You may. That is, both the first marker M1 and the pair of second markers M2a and M2b are formed by ejecting ink from the same nozzle row 6Ak of the recording head 6A.

Further, for example, the pattern forming unit 111 ejects ink from nozzles in a row different from that of the first marker M1 among the four rows (plurality) of nozzle rows of the recording head 6A to form a pair of second markers M2a and M2b. May form. That is, the first marker M1 is formed by ejecting ink from the nozzle row 6Ak of the recording head 6A, and the pair of second markers M2a and M2b are formed by ejecting ink from the nozzle row 6Am of the recording head 6A. In this case, the pair of second markers M2a and M2b are displaced in the main scanning direction, but can be formed at positions separated by a distance e from the reference nozzle in the front-rear direction in the sub-scanning direction.

Here, the test pattern TP may have a configuration in which the first marker M1 is formed before the predetermined transport amount L1 is transported, and a pair of second markers M2a and M2b are formed after the predetermined transport amount L1 is transported. The positional relationship between the first marker M1 and the pair of second markers M2a and M2b can be arbitrarily set. Further, the position and timing of forming each of the first marker M1 and the pair of second markers M2a and M2b included in the test pattern TP (this timing determines whether the carriage 5 is formed during the outward movement or the return movement). Is indicated by the pattern data above.

Further, the pattern forming unit 111 may form a pair of second markers M2a and M2b after forming the first marker M1 on the recording medium P and transporting the recording medium P with an actual transport amount L1 which is an integral multiple. Good. Specifically, the ideal transport amount L2, which is the distance between the nozzle forming the first marker M1 and the reference nozzle, is set to an integral multiple (n times) (n × L2), and the recording medium is recorded after the formation of the first marker M1. P may be configured to be transported by n × actual transport amount L1. In this case, by transporting with n × the actual transport amount L1, the influence of the error due to the bending of the nozzle used for forming the marker is dispersed to a distance n times. That is, the error due to nozzle bending or the like becomes 1 / n, and the error can be reduced. When the ideal transport amount L2 is small or the formation width in the sub-scanning direction is large, it is possible to obtain a more accurate displacement amount by multiplying the actual transport amount L1 by n when forming the test pattern TP. .. When the effect of nozzle bending is so small that it can be ignored, it is not necessary to disperse the error of nozzle bending and take the average as described above.

Returning to FIG. 14, the position detection unit 142 of the CPU 140 for the two-dimensional sensor performs a predetermined process such as binarization on the image captured by the image pickup unit 20 to obtain the first marker M1 from the captured image. And a pair of second markers M2a and M2b are detected, respectively.

The ratio calculation unit 143 of the CPU 140 for a two-dimensional sensor determines the distance between the pair of second markers M2a and M2b in the captured image and the distance between the pair of second markers M2a and M2b in the captured image based on the positions of the first marker M1 and the pair of second markers M2a and M2b in the captured image. The ratio of the first marker M1 to the amount of misalignment in the captured image is calculated.

Specifically, a method of calculating the ratio will be described with reference to FIG. FIG. 17 is an explanatory diagram of a method of calculating the ratio of the distance between the pair of second markers M2a and M2b in the captured image and the amount of misalignment of the first marker M1. As shown in FIG. 17, the ratio calculation unit 143 obtains the distance 2D of the pair of second markers M2a and M2b in the captured image from the detected positions of the pair of second markers M2a and M2b. Then, the amount of misalignment s of the first marker M1 in the captured image is obtained from the difference between the detected position of the first marker M1 and the ideal position of the first marker M1. Here, the ideal position of the first marker M1 is a pair of positions corresponding to the middle between the pair of second markers M2a and M2b in the present embodiment, that is, from the respective positions of the second marker M2a and the second marker M2b. It is a position at a distance of 1/2 of the distance between the second markers M2a and M2b. In FIG. 17, it is a position equidistant D from each position of the second marker M2a and the second marker M2b (the position of the dotted line in FIG. 17). Then, the ratio is calculated by dividing the misalignment amount s of the first marker M1 in the captured image by the distance 2D between the pair of second markers M2a and M2b in the captured image. The above ratio calculated by the ratio calculation unit 143 is passed to the actual distance calculation unit 114.

Here, consider a case where a relative positional deviation occurs between the first marker M1 and the pair of second markers M2a and M2b when the test pattern TP illustrated in FIG. 15 is formed on the recording medium P. FIG. 18 is a diagram illustrating an example in which a relative positional deviation occurs between the first marker M1 included in the test pattern and the pair of second markers M2a and M2b.

In the test pattern TP illustrated in FIG. 15, as described above, the first marker M1 should be formed at a position (ideal position) corresponding to the middle between the pair of second markers M2a and M2b, but the recording medium. As shown in FIG. 18, it is assumed that the first marker M1 is formed at a position close to the second marker M2a due to the deviation of the ink landing position due to the fluctuation of the transport amount of P. At this time, the distance between the first marker M1 and the second marker M2b on the captured image is a, and the distance between the first marker M1 and the second marker M2a on the captured image is b.

Even if a relative positional deviation occurs between the pair of second markers M2a and M2b and the first marker M1, the pair of second markers M2a and M2b are formed under the same conditions (the same amount of transport). Therefore, there is no change in the actual distance between the pair of second markers M2a and M2b. That is, the actual distance corresponding to the distance a + b (distance between the pair of second markers M2a and M2b) in FIG. 18 has a relative positional deviation between the pair of second markers M2a and M2b and the first marker M1. It does not change even if it occurs.

FIG. 19 is a diagram for explaining the amount of misalignment of the first marker M1 with respect to the pair of second markers M2a and M2b. In FIG. 19, each of the pair of second markers M2a and M2b has coordinates with the midpoint between the pair of second markers M2a and M2b as the origin, the actual distance as the horizontal axis, and the distance on the captured image as the vertical axis. It is a plot of the position. In the example of FIG. 19, it is assumed that the relative misalignment as shown in FIG. 18 occurs between the pair of second markers M2a and M2b and the first marker M1.

In FIG. 19, the inclination of the straight line connecting the positions of the pair of second markers M2a and M2b plotted is the distance between the pair of second markers M2a and M2b and the distance between the pair of second markers M2a and M2b in the captured image. It corresponds to the ratio with the actual distance. That is, the slope of this straight line represents the ratio (image magnification) of the distance to the actual distance in the captured image. Further, since the position of the first marker M1 is the origin when there is no relative positional deviation between the pair of second markers M2a and M2b and the first marker M1, the pair of plotted second markers The distance s between the intersection of the straight line connecting the positions of M2a and M2b and the horizontal axis and the origin is the amount of misalignment of the first marker M1 with respect to the pair of second markers M2a and M2b.

The ratio of the distance to the actual distance (image magnification) in the above-mentioned captured image changes depending on the fluctuation of the distance between the imaging unit 20 and the test pattern TP. As described above, the image forming apparatus 100 of the present embodiment has a configuration in which the recording medium P on which the test pattern TP is formed is supported on the platen 16 having the uneven shape in which the rib-shaped protrusions are formed. The distance between the imaging unit 20 and the test pattern TP fluctuates due to the influence of the uneven shape of the platen 16, and this ratio may change.

FIG. 20 is a diagram for explaining the amount of misalignment of the first marker M1 with respect to the pair of second markers M2a and M2b when the distance between the imaging unit and the test pattern fluctuates. When the distance between the image pickup unit 20 and the test pattern TP becomes smaller, the distance between the second marker M2b and the first marker M1 on the captured image becomes a'a'larger value than a shown in FIG. The distance between the second marker M2a and the first marker M1 on the image is b', which is larger than b shown in FIG. Therefore, the slope of the straight line connecting the positions of the pair of second markers M2a and M2b plotted is larger than that in the example of FIG.

On the other hand, when the distance between the imaging unit 20 and the test pattern TP increases, the distance between the second marker M2b and the first marker M1 on the captured image is a'', which is smaller than a shown in FIG. Therefore, the distance between the second marker M2a and the first marker M1 on the captured image is b'', which is smaller than b shown in FIG. Therefore, the slope of the straight line connecting the positions of the pair of second markers M2a and M2b plotted is smaller than that in the example of FIG. However, the amount of misalignment s of the first marker M1 with respect to the pair of second markers M2a and M2b does not change even if the inclination of the straight line connecting the positions of the pair of second markers M2a and M2b changes.

Further, the distance between the intersection of the straight line connecting the positions of the paired second markers M2a and M2b plotted and the vertical axis and the origin is the position of the first marker M1 with respect to the pair of second markers M2a and M2b in the captured image. The amount of deviation. As the distance between the imaging unit 20 and the test pattern TP decreases, the distance between the pair of second markers M2a and M2b increases, but the amount of misalignment in the captured image also increases in proportion. On the other hand, as the distance between the imaging unit 20 and the test pattern TP increases, the distance between the pair of second markers M2a and M2b decreases, but the amount of misalignment in the captured image also decreases by the same ratio. That is, even if the distance between the image pickup unit and the test pattern fluctuates, the ratio between the distance between the pair of second markers M2a and M2b and the amount of misalignment in the captured image does not change.

Returning to FIG. 14, the actual distance calculation unit 114 of the CPU 110 multiplies the actual distance between the pair of second markers M2a and M2b by the ratio calculated by the ratio calculation unit 143 with respect to the pair of second markers M2a and M2b. The actual distance of the misalignment amount s of the first marker M1 is calculated. The actual distance calculated by the actual distance calculation unit 114 is passed to the adjustment unit 115.

The adjusting unit 115 of the CPU 110 calculates and calculates the correction amount of the parameter related to the transport amount of the recording medium P by the transport control unit 116 based on the misalignment amount s of the first marker M1 calculated by the actual distance calculation unit 114. Adjust according to the corrected amount. The parameter related to the transport amount of the recording medium P is, for example, a parameter for controlling the rotation speed for rotating the transport roller 152. The adjusting unit 115 adjusts the control operation of the transport roller 152 by the transport control unit 116 and the like by transmitting the adjusted values of these parameters to the control FPGA 120.

<Operation of image forming device>
Next, with reference to FIG. 21, an outline of the operation related to the adjustment of the transport amount of the image forming apparatus 100 will be described. FIG. 21 is a flowchart showing a flow of operations related to adjustment of a transport amount in the image forming apparatus of the first embodiment.

When the recording medium P is set on the platen 16, the pattern forming unit 111 of the CPU 110 first forms the first marker M1 on the recording medium P (step S10). Then, the transport control unit 116 of the CPU 110 transports the recording medium P with a predetermined actual transport amount L1 (step S11).

Next, the pattern forming unit 111 is paired on the recording medium P by a designated nozzle separated by a distance e in the sub-scanning direction from a reference nozzle separated by an ideal transfer amount L2 from the nozzle forming the first marker M1. The second markers M2a and M2b are formed (step S12). As a result, a test pattern TP including the first marker M1 and the pair of second markers M2a and M2b is formed.

Next, the two-dimensional sensor 27 of the imaging unit 20 images the test pattern TP formed in steps S10 and S12, and outputs the captured image of the test pattern TP (step S13). The position detection unit 142 of the two-dimensional sensor CPU 140 detects the positions of the pair of second markers M2a and M2b and the first marker M1 in the captured image, respectively (step S14).

Next, the ratio calculation unit 143 of the CPU 140 for the two-dimensional sensor uses the positions of the detected first marker M1 and the pair of second markers M2a and M2b in the captured image to use the paired second markers M2a in the captured image. The ratio between the distance between M2b and the amount of misalignment of the first marker M1 in the captured image is calculated (step S15).

Next, the actual distance calculation unit 114 of the CPU 110 uses the pattern data used for forming the test pattern TP in steps S10 and S12 and the ratio calculated in step S15 between the pair of second markers M2a and M2b. The actual distance of the first marker M1 is multiplied by the above ratio to calculate the actual distance of the amount of misalignment of the first marker M1 (step S16).

Next, the adjusting unit 115 of the CPU 110 determines whether or not the ink landing position shift has occurred based on the actual distance of the position shift amount of the first marker M1 calculated in step S16 (step S17). If it is determined that the ink landing position shift does not occur (step S17: No), the series of operations ends as it is.

On the other hand, when it is determined that the ink landing position shift has occurred (step S17: Yes), the adjusting unit 115 determines that the position shift amount of the first marker M1 calculated in step S16 is based on the actual distance. The correction amount of the parameter related to the transport amount of the recording medium P is calculated (step S18). Then, the parameter related to the conveyed amount of the recording medium P is adjusted according to the calculated correction amount (step S19), and the series of operations is completed.

As described above, the image forming apparatus 100 of the present embodiment transports the recording medium P with a predetermined transport amount (actual transport amount L1) after forming the first marker M1 to carry the pair of second markers M2a and M2b. By forming, a test pattern TP including the first marker M1 and the pair of second markers M2a and M2b is formed. Then, the test pattern TP is imaged by the imaging unit 20. Next, the positions of the pair of second markers M2a and M2b and the first marker M1 of the test pattern TP in the captured image are detected, respectively. Then, the ratio of the distance between the pair of second markers M2a and M2b in the captured image and the amount of misalignment of the first marker M1 in the captured image is calculated, and the actual distance between the pair of second markers M2a and M2b is calculated as described above. The actual distance of the amount of misalignment of the first marker M1 is calculated by multiplying the ratio of. Then, the parameters related to the conveyed amount of the recording medium P are adjusted according to the actual distance of the displaced amount.

Therefore, according to the image forming apparatus 100 of the present embodiment, even in an environment where the distance between the image pickup unit 20 and the test pattern TP fluctuates, the ink landing based on the captured image obtained by capturing the test pattern TP. The actual distance according to the amount of misalignment can be appropriately calculated, and the image quality can be improved by adjusting the parameters related to the amount of transport of the recording medium P according to the amount of misalignment.

<Other calculation methods of the actual distance of the displacement amount of the first marker>
In the above-described embodiment, the ratio between the distance between the pair of second markers M2a and M2b in the captured image and the amount of misalignment of the first marker M1 in the captured image is calculated, and the actual result between the pair of second markers M2a and M2b is calculated. The actual distance of the misalignment amount of the first marker M1 was calculated by calculating the ratio to the distance, but the actual distance of the misalignment amount of the first marker M1 was calculated by the following method. You may.

The ratio calculation unit 143 calculates the ratio between the distance between the pair of second markers M2a and M2b in the captured image and the distance between one of the pair of second markers M2a and M2b in the captured image and the first marker M1. To do. For example, referring to FIG. 18, a / a + b or b / a + b is the ratio calculated here.

Then, the actual distance calculation unit 114 multiplies the actual distance between the pair of second markers M2a and M2b by the ratio calculated by the ratio calculation unit 143 to obtain one of the pair of second markers M2a and M2b. The actual distance of the distance from the first marker M1 is calculated. Then, with one of the pair of second markers M2a and M2b calculated from the distance between the first marker M1 and one of the pair of second markers M2a and M2b in the pattern data used for forming the test pattern TP. By subtracting the actual distance of the distance from the first marker M1, the actual distance of the amount of misalignment of the first marker M1 is calculated. Then, based on the calculated actual distance of the displacement amount of the first marker M1, the parameter related to the transport amount of the recording medium P can be adjusted.

<Modification example of test pattern>
The test pattern TP used in this embodiment is not limited to the example shown in FIG. 15, and can be variously modified. Hereinafter, a modified example of such a test pattern TP will be described.

The test pattern TP illustrated in FIG. 15 has a configuration in which a pair of second markers M2a, M2b and a first marker M1 are formed as dots, but the pair of second markers M2a, M2b and the first marker M1 are combined with the carriage 5. It may be formed in a linear shape extending in the main scanning direction, which is the moving direction of the. FIG. 22 is a diagram showing an example of a test pattern formed by linear markers. For example, as shown in FIG. 22, a pair of second markers M2a and M2b and a pair of second markers M2a and M2b are linearly extending in the main scanning direction (direction of arrow A in the figure), and the pair of second markers M2a and M2b. The first marker M1 may be formed between them. By forming the markers linearly in this way, it becomes easy to detect the position of the markers in the captured image.

Further, the test pattern TP may be configured to form a plurality of linear markers extending in the main scanning direction. FIG. 23 is a diagram showing an example of a test pattern formed by a plurality of linear markers. For example, as shown in FIG. 23, the pair of second markers M2a, M2b and the first marker M1 are linear with a predetermined length extending in the main scanning direction (direction of arrow A in the figure), and the pair of second markers. The first marker M1 is formed between the markers M2a and M2b. Then, a plurality of test pattern TPs may be arranged in a plurality of marker sets M in the main scanning direction (4 sets in FIG. 23). In FIG. 23, a plurality of first markers M1 ″ to M1 ″ ″, second markers M2a ″ to M2a ″ ″, and M2b ″ to M2b ″ ″ are formed by different nozzles.

As described above, when a set M of a plurality of markers composed of lines extending in the main scanning direction is formed by one nozzle, it may be affected by the ejection bending peculiar to the nozzle. However, it is possible to reduce the influence of the nozzle-specific discharge bending by forming a plurality of marker sets M with different nozzles, calculating the amount of misalignment from the test pattern TP formed by different nozzles, and averaging them. it can. Specifically, for example, in FIG. 23, since the amount of misalignment is obtained from the test pattern TP in which four sets of markers M are formed, the error can be reduced to 1/4.

Further, a test pattern TP in which a plurality of linear markers extending in the main scanning direction are arranged is formed, and a reference line serving as a reference for specifying the positions of the first marker M1 and the pair of second markers M2a and M2b is set as the first marker. The configuration may be formed under conditions different from those of the second markers M2a and M2b paired with M1. The reference line may be a reference frame surrounding the first marker M1 and the pair of second markers M2a and M2b.

FIG. 24 is a diagram showing an example of a test pattern and a reference frame formed by a plurality of linear markers. In FIG. 24, in addition to the test pattern TP of FIG. 23, a reference frame F surrounding the test pattern TP is formed. The reference frame F is formed of, for example, a line having a thickness different from that of the test pattern TP, as a condition different from the line of the marker of the test pattern TP. Therefore, when detecting the positions of the first marker M1 and the pair of the second markers M2a and M2b in the captured image, the reference frame F is distinguished from the test pattern TP composed of the first marker M1 and the pair of the second markers M2a and M2b. Can be done.

After acquiring the captured image, the image forming apparatus 100 first detects the position of the reference frame F. Then, by detecting the positions of the first marker M1 and the pair of second markers M2a and M2b based on the position of the reference frame F, even if the position of forming the test pattern TP in the captured image is deviated, the first marker M1 is detected. The positions of the one marker M1 and the pair of second markers M2a and M2b can be easily detected.

Here, the reference frame F will be described. When imaging is performed by the imaging unit 20 that does not have the reference chart 300 (see FIGS. 9) (see FIGS. 10 and 11), it is desirable to set the imaging range so that the reference frame F is located near the center of the imaging range. Further, when an image is taken by the imaging unit 20 having the reference chart 300 (see FIGS. 4 to 8), the image is emitted from the light source 58 at a position where the image can be taken from the opening 53 in the imaging range where the reference chart 300 is not provided. It is desirable to set the imaging range so that the reference frame F is located near the optical axis of light.

With reference to FIG. 25, an outline of the operation related to the adjustment of the transport amount of the image forming apparatus 100 when the test pattern TP and the reference frame F as shown in FIG. 24 are formed will be described. FIG. 25 is a flowchart showing the flow of operations related to the adjustment of the transport amount in the image forming apparatus of the modified example of the first embodiment.

When the recording medium P is set on the platen 16, the pattern forming unit 111 of the CPU 110 first forms the first marker M1 on the recording medium P, and forms the reference frame F with an arbitrary nozzle (step S30). .. Then, the transport control unit 116 of the CPU 110 transports the recording medium P with a predetermined actual transport amount L1 (step S31).

Next, the pattern forming unit 111 is paired on the recording medium P by a designated nozzle separated by a distance e in the sub-scanning direction from a reference nozzle separated by an ideal transfer amount L2 from the nozzle forming the first marker M1. The second markers M2a and M2b are formed (step S32). As a result, the test pattern TP including the first marker M1 and the pair of second markers M2a and M2b and the reference frame F are formed.

Next, the two-dimensional sensor 27 of the imaging unit 20 images the test pattern TP and the reference frame F formed in steps S30 and 32, and outputs the captured images of the test pattern TP and the reference frame F (step S33).

Next, the position detection unit 142 of the CPU 140 for the two-dimensional sensor analyzes the captured image of the test pattern TP and the reference frame F output in step S33, and determines whether or not the reference frame F is within the imaging range. (Step S34).

When there is a reference frame F (step S34: Yes), the position detection unit 142 identifies the reference frame F and determines whether or not a predetermined number of markers are present in the reference frame F (step S35). When a specified number of markers are present (step S35: Yes), the position detection unit 142 identifies the positions of the pair of second markers M2a, M2b and the first marker M1 based on the reference frame F in the captured image, and respectively. Detect (step S36).

On the other hand, when there is no reference frame F in step S34 (step S34: No) and when the specified number of markers does not exist in the reference frame F in step S35 (step S35: No), the position detection unit 142 causes an error. The determination (step S37) is made, and the process ends.

Next, the processes (steps S38 to 42) from the calculation of the ratio by the ratio calculation unit 143 of the two-dimensional sensor CPU 140 to the adjustment of the parameters related to the transport amount by the adjustment unit 115 are the same as those in the first embodiment. Therefore, the description thereof will be omitted (see steps S15 to 19 in FIG. 21). In FIG. 25, the reference frame F is formed together with the first marker M1, but the reference frame F may be formed before the formation of the test pattern TP, or after the formation of the test pattern TP and before imaging. May be formed in.

When the reference frame F is formed together with the test pattern TP in this way, the reference frame F is specified from the captured image captured by the imaging unit 20, and the pair of first markers M1a, M1b and the first markers M1a, M1b and the first are based on the reference frame F. Since the position of the two marker M2 is specified and detected, the position of the test pattern TP in the captured image can be easily specified.

(Second Embodiment)
The image forming apparatus of the first embodiment has a configuration in which the CPU for the two-dimensional sensor mounted on the carriage performs the position detection processing of the test pattern from the captured image and the ratio calculation processing, but the position detection processing And the ratio calculation process may be performed on the main control board.

First, the hardware configuration of the image forming apparatus 200 of the present embodiment will be described with reference to FIG. 26. FIG. 26 is a hardware configuration diagram of the image forming apparatus of the second embodiment.

As shown in FIG. 26, the image forming apparatus 200 of the present embodiment includes a CPU 210, a ROM 102, a RAM 103, a recording head driver 104, a main scanning driver 105, a sub scanning driver 106, a control FPGA 120, a recording head 6, and a main scanning encoder sensor. It includes 131, an imaging unit 40, a main scanning motor 8, a transport unit 150, and a sub-scanning motor 12.

The CPU 210, ROM 102, RAM 103, recording head driver 104, main scanning driver 105, sub-scanning driver 106, and control FPGA 120 are mounted on the main control board 230. Further, the recording head 6, the main scanning encoder sensor 131, and the imaging unit 40 are mounted on the carriage 50. Further, the sub-scanning encoder sensor 132 and the transfer roller 152 are mounted on the transfer unit 150 described above.

Here, the description is omitted because the configuration is the same as that of the first embodiment except for the configuration of the CPU 210 and the imaging unit 40.

The CPU 210 controls the entire image forming apparatus 200 as in the first embodiment. In particular, in the image forming apparatus 200 of the present embodiment, the CPU 210 provides a function of forming a test pattern TP, a function of a distance measuring apparatus, a function of adjusting parameters related to the amount of transport of the recording medium P based on the distance, and the like. Realize.

The imaging unit 40 captures a test pattern TP (see FIG. 15) formed on the recording medium P under the control of the CPU 210, and includes a two-dimensional sensor 27.

As described above, the two-dimensional sensor 27 is a CCD sensor, a CMOS sensor, or the like, and images the test pattern TP under predetermined operating conditions based on various setting signals sent from the CPU 210 via the control FPGA 120. Then, the two-dimensional sensor 27 outputs the captured image to the CPU 210 via the control FPGA 120.

Next, with reference to FIG. 27, the characteristic functions realized by the CPU 210 of the image forming apparatus 200 will be described. FIG. 27 is a block diagram showing a functional configuration of the image forming apparatus of the second embodiment.

The CPU 210 uses, for example, the RAM 103 as a work area and executes a control program stored in the ROM 102 to execute a pattern forming unit 111, a position detecting unit 212, a ratio calculation unit 213, an actual distance calculation unit 114, and an adjusting unit. It realizes functions such as 115 and the transport control unit 116.

Here, since the functions of the pattern forming unit 111, the actual distance calculation unit 114, the adjusting unit 115, and the transport control unit 116 are the same as those of the first embodiment, the description thereof will be omitted.

Further, the functions of the position detection unit 212 and the ratio calculation unit 213 are the same as those of the position detection unit 142 and the ratio calculation unit 143 of the first embodiment, but unlike the first embodiment, they are executed by the CPU 210. ..

The flow of the operation related to the adjustment of the transport amount at the image forming position in the image forming apparatus 200 of the second embodiment is the same as that of the first embodiment, and thus the description thereof will be omitted (see FIG. 21).

As described above, in the image forming apparatus 200 of the present embodiment, all the functions including the position detecting unit 212 and the ratio calculation unit 213 are performed by the CPU 210 of the main control board 230. Even when configured in this way, the same effect as that of the image forming apparatus 100 of the first embodiment is obtained.

The program executed by the image forming apparatus of the present embodiment is provided by being incorporated in a ROM or the like in advance. The program executed by the image forming apparatus of the present embodiment is a file in an installable format or an executable format on a computer such as a CD-ROM, a flexible disc (FD), a CD-R, or a DVD (Digital Versatile Disc). It may be configured to be recorded and provided on a readable recording medium.

Further, the program executed by the image forming apparatus of the present embodiment may be stored on a computer connected to a network such as the Internet and provided by downloading via the network. Further, the program executed by the image forming apparatus of the present embodiment may be configured to be provided or distributed via a network such as the Internet.

The program executed by the image forming apparatus of the present embodiment has a module configuration including each of the above-mentioned parts (pattern forming part, position detecting part, ratio calculation part, actual distance calculation part, adjustment part, transfer control part). As the actual hardware, the CPU (processor) reads the program from the ROM and executes it, so that each part is loaded on the main memory and each part is generated on the main memory. .. Further, for example, a part or all of the functions of the above-mentioned parts may be realized by a dedicated hardware circuit.

Although the specific embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments as they are, and various modifications and changes are made at the implementation stage without departing from the gist thereof. However, it can be materialized.

For example, in the above-described embodiment, an example of application to an image forming apparatus configured as a serial head type inkjet printer has been described, but the present invention can be applied to various types of image forming apparatus. For example, in a line head type inkjet printer, the ink landing position shift may occur due to the position shift between the recording heads. By applying the present invention, when such an ink landing misalignment occurs, the misalignment amount can be correctly obtained, and the parameter related to the transport amount of the recording medium can be adjusted according to the misalignment amount. Therefore, the image quality can be improved.

Further, for example, in a tandem type electrophotographic image forming apparatus, an image misalignment corresponding to an ink landing misalignment in an inkjet printer occurs due to a misalignment of a photoconductor drum forming an image of each color. obtain. By applying the present invention, when such an image misalignment occurs, the misalignment amount can be correctly obtained, and by adjusting the parameters related to the transport amount of the recording medium according to the misalignment amount. , Image quality can be improved.

Further, for example, in a thermal printer that prints on a recording medium by heat, an image misalignment corresponding to an ink landing position misalignment in an inkjet printer may occur due to a misalignment of the thermal head or the like. By applying the present invention, when such an image misalignment occurs, the misalignment amount can be correctly obtained, and by adjusting the parameters related to the transport amount of the recording medium according to the misalignment amount. , Image quality can be improved.

Further, the image formation of the present embodiment includes not only output to a recording medium such as paper but also formation of a substrate. In the above embodiment, the image forming apparatus of the present invention has been described with reference to an example applied to a printer, but a multifunction device, a copying machine, etc. having at least two functions of a copy function, a printer function, a scanner function, and a facsimile function have been described. It can also be applied to the image forming apparatus of.

5, 50 Carriage 6 (6A, 6B, 6C) Recording head 20, 40 Imaging unit 27 Two-dimensional sensor 28 Imaging lens 100, 200 Image forming apparatus 110 CPU
111 Pattern forming unit 114 Actual distance calculation unit 115 Adjustment unit 116 Transport control unit 140 CPU for 2D sensor
142, 212 Position detection unit 143, 213 Ratio calculation unit 150 Transport unit P Recording medium TP test pattern M1 1st marker M2a, M2b 2nd marker

Japanese Patent No. 5392055

Claims (12)

A transport control unit that transports the object to be transported,
An image forming unit that forms an image on the transported object,
Using the image forming unit, either the first marker or the pair of second markers is formed on the object to be transported, and the object to be transported is formed after being transported by a predetermined transport amount and before being transported. A pattern forming portion that forms either the first marker and the pair of second markers.
An imaging unit that captures a test pattern including the first marker and the pair of second markers.
A position detection unit that detects the positions of the first marker and the pair of second markers in the captured image captured by the imaging unit, and a position detection unit.
A ratio calculation unit that calculates the ratio between the distance between the pair of second markers in the captured image and the amount of misalignment of the first marker in the captured image.
An actual distance calculation unit that calculates the actual distance of the amount of misalignment of the first marker based on the actual distance between the pair of second markers and the ratio.
An image forming apparatus. The image forming apparatus according to claim 1, further comprising an adjusting unit that adjusts a parameter related to the amount of the transported object by the transport control unit according to the calculated actual distance of the misaligned amount of the first marker. The image forming unit includes a recording head that ejects ink.
According to claim 1 or 2 , the pattern forming unit ejects ink from nozzles in the same row among a plurality of nozzle rows included in the recording head to form the first marker and the pair of second markers. The image forming apparatus according to the description. The image forming unit includes a recording head that ejects ink.
The pattern forming unit according to claim 1 or 2 , wherein ink is ejected from nozzles in different rows among a plurality of nozzle rows included in the recording head to form the first marker and the pair of second markers. The image forming apparatus according to the description. The image forming apparatus according to claim 3 or 4 , wherein the first marker and the pair of second markers are formed along the transport direction of the object to be transported. The image forming unit includes a recording head for ejecting ink and a carriage on which the recording head is mounted and reciprocates.
Claim 1 or 2 in which the pattern forming unit ejects ink from a nozzle of the recording head to form the first marker and the pair of second markers in a linear shape extending in the moving direction of the carriage. The image forming apparatus according to. The pattern forming portion, among the plurality of nozzles the recording head has, by ejecting ink from different nozzles to form a plurality of the first marker and a plurality of the pair of second marker, in claim 6 The image forming apparatus according to the description. The pattern forming unit forms the first marker on the object to be transported, forms the pair of second markers after the object to be transported is transported by the predetermined transport amount, and forms the pair of second markers.
The pair of second markers are formed by two nozzles separated by a predetermined distance on both front and rear sides in the transport direction of the object to be transported, with reference to a nozzle separated by an ideal transport amount from the nozzle forming the first marker. The image forming apparatus according to any one of claims 3 to 7. The pattern forming unit forms a reference line for identifying the positions of the first marker and the pair of second markers under different conditions from the first marker and the pair of second markers. 8. The image forming apparatus according to any one of 8. The image forming apparatus according to claim 9 , wherein the reference line is a reference frame surrounding the first marker and the pair of second markers. A transport control unit that transports the object to be transported,
An image forming unit that forms an image on the transported object,
Using the image forming unit, either the first marker or the pair of second markers is formed on the object to be transported, and the object to be transported is formed after being transported by a predetermined transport amount and before being transported. A pattern forming portion that forms either the first marker and the pair of second markers.
An imaging unit that captures a test pattern including the first marker and the pair of second markers.
A position detection unit that detects the positions of the first marker and the pair of second markers in the captured image captured by the imaging unit, and a position detection unit.
A ratio calculation unit that calculates the ratio between the distance between the pair of second markers in the captured image and the distance between one of the pair of second markers in the captured image and the distance between the first marker.
The actual distance of the amount of misalignment of the first marker based on the actual distance between the pair of second markers, the ratio, and the actual distance of one of the pair of second markers and the first marker. The actual distance calculation unit that calculates
An image forming apparatus. A transport control step for transporting the object to be transported and
An image forming step of forming an image on the conveyed object,
One of the first marker and the pair of second markers is formed on the transported object, and after the transported object is transported by a predetermined transport amount, the first marker and the pair are not formed before the transport. A pattern forming step that forms one of the second markers of
An imaging step of imaging a test pattern including the first marker and the pair of second markers.
A position detection step for detecting the positions of the first marker and the pair of second markers in the captured image, and a position detection step.
A ratio calculation step for calculating the ratio between the distance between the pair of second markers in the captured image and the displacement amount of the first marker in the captured image.
An actual distance calculation step of calculating the actual distance of the amount of misalignment of the first marker based on the actual distance between the pair of second markers and the ratio.
A program that lets your computer run.

Images