JP2014028463A - Image forming apparatus, pattern position detection method, image formation system, and method for producing printed matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus for detecting a discharge position of ink having color similar to color of a recording medium or a discharge position of ink, the position of which cannot be detected by the conventional method since reflection intensity is large.SOLUTION: The image forming apparatus for reading a test pattern, and adjusting ink discharge timing, includes: test pattern formation means for reading first pattern data having a solid pattern of first ink and a reference line, and second pattern data having two lines to form a test pattern; and position detection means for detecting the position of a line obtained by performing a line position determination calculation of intensity data. The test pattern formation means forms one molding line by being formed on an edge of a solid pattern after forming the solid pattern and a reference line on the basis of the first pattern data, and forms two lines so that an interval between a line center of the reference line and a line center of the molding line becomes a predetermined distance.

Description

  The present invention relates to an image forming apparatus that reads a test pattern of a plurality of lines formed on a recording medium and adjusts a droplet discharge timing.

  2. Description of the Related Art There is known an image forming apparatus that produces droplets by ejecting droplets onto a sheet material such as paper to produce a printed material (hereinafter referred to as a liquid ejection type image forming apparatus). Such an image forming apparatus produces printed matter by forming an image on the entire paper by reciprocating the recording head perpendicularly to the paper feeding direction (in the main scanning direction) while repeating paper feeding (in a serial system). Image forming apparatus).

  However, it is known that when the image forming apparatus forms one ruled line in both forward and backward directions, the ruled line is likely to be misaligned in the forward and return paths.

  In addition, even in a line type image forming apparatus in which nozzles are arranged to be approximately the same length as the maximum sheet width, the droplet landing position may be shifted due to nozzle processing accuracy, mounting error, or the like. Are known.

  Conventionally, the user manually corrects the positional deviation (see, for example, Patent Document 1). Patent Document 1 discloses an image forming apparatus in which a correction value is also printed on an adjustment pattern when an adjustment pattern for misregistration correction is printed, and the user selects an adjustment pattern with a small misregistration and inputs a correction value numerically. It is disclosed.

  In addition, an image forming apparatus equipped with an adjustment function that adjusts the landing position of a droplet instead of being manually corrected by a user is also considered (for example, see Patent Document 2). In Patent Document 2, a water-repellent member having water repellency is composed of a reference pattern composed of a plurality of independent droplets and a plurality of independent droplets ejected under ejection conditions different from the reference pattern. Reading means comprising a pattern forming means for forming the measured patterns side by side in the scanning direction of the recording head, a light emitting means for irradiating each pattern with light, and a light receiving means for receiving specularly reflected light from each pattern And a correction unit that measures the distance between the patterns based on the reading result of the reading unit and corrects the droplet discharge timing of the recording head based on the measurement result. Has been.

  However, since the conventional adjustment method does not consider the reflection intensity that can change according to the color of the ink, there is a problem that it is difficult to perform accurate positional deviation correction depending on the combination of the recording medium and the color of the ink. .

  For example, when measuring reflected light from a test pattern as described in Patent Document 2, the image forming apparatus uses a color ink that easily absorbs light such as black or magenta on a recording medium such as paper. Can be considered.

  FIG. 26A is a diagram showing an example of the relationship between a general test pattern and the intensity of reflected light. The light emitting element emits the spot light, and the light receiving element receives the reflected light of the spot light and converts it into a voltage value. The image forming apparatus detects the line center (the center position of the line obtained from the boundary position between the recording medium and the pattern) by utilizing the fact that the intensity of the reflected light of the pattern forming portion is sharply reduced from the exposed portion of the recording medium. To do.

  On the other hand, for example, when the recording medium is white like plain paper and a white ink pattern (white line) is formed, the white ink has a high reflection intensity, so the line center of the white line must be accurately identified. Is in difficulty.

  FIG. 26B is a diagram showing an example of the relationship between the test pattern in which black and white lines are formed and the intensity of reflected light. The voltage when the spot light scans black rapidly decreases, but no significant decrease is seen in the voltage when the white line is scanned. Thus, when a test pattern is formed on plain paper, it is difficult to adjust the discharge timing of white ink. Even when the color of the recording medium is other than white, the same problem may occur when the color of the ink is similar to the color of the recording medium.

  Even when the recording medium and the ink color are not the same system, the white line position is difficult to detect because the reflection intensity of the white line is high. The same is true for inks of other colors with high reflection intensity. If a white line is formed on a black or other recording medium, the reflected light larger than the ground color portion is detected because the white line has a high reflection intensity. However, as shown in FIG. 26 (a), the intensity of the reflected light from the white line does not decrease (because it becomes relatively large), so the calculation method is changed to detect the position of the line. Necessity arises. Thus, the color of the ink having a high reflection intensity such as white cannot accurately detect the line position by the same method as the conventional one.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an image forming apparatus that detects an ink ejection position of a color similar to the color of a recording medium or an ink ejection position that cannot be detected by a conventional method because of high reflection intensity. For the purpose.

In view of the above problems, the present invention provides an image forming apparatus that reads a test pattern formed of a plurality of lines formed on a recording medium and adjusts the ink ejection timing, and a light emitting unit that irradiates the recording medium with light. Reading means having light receiving means for receiving reflected light from the recording medium, pattern data storage means for storing pattern data for forming the test pattern, and a first whose reflection intensity is not more than a first threshold value The first pattern data having the solid ink pattern and the reference line and the second pattern data having the two lines of the second ink having a reflection intensity equal to or higher than the second threshold are read out to form a test pattern. Test pattern forming means, relative movement means for moving the recording medium or the reading means at a relatively constant speed, and a test pattern And intensity data storing means for the light receiving means for storing the intensity data of the reflected light received from the scanning position of the light while the above said light is moving,
Position detecting means for performing a line position determination operation on the intensity data included within a lower limit from a predetermined upper limit to detect the position of the line, and the test pattern forming means includes the first pattern data After forming the solid pattern and the reference line on the basis of the above, it is formed on the edge of the solid pattern to form one molding line, and the distance between the line center of the reference line and the line center of the molding line is The two lines are formed so as to have a predetermined distance.

  It is possible to provide an image forming apparatus that detects an ink ejection position of a color similar to the color of a recording medium or an ink ejection position that cannot be detected by a conventional method because of a high reflection intensity.

It is an example of the figure explaining the outline of the formation method of a test pattern. It is an example of the figure which shows the relationship between the position of a white line, and the intensity | strength of reflected light. 1 is an example of a schematic perspective view of a serial type image forming apparatus. It is an example of the figure explaining the operation | movement of a carriage in detail. 2 is an example of a block diagram of a control unit of the image forming apparatus. FIG. FIG. 2 is an example of a diagram schematically illustrating a configuration for a print position deviation sensor to detect an edge of a test pattern. It is an example of a functional block diagram of a correction processing execution unit It is an example of the figure explaining a test pattern. It is an example of the figure explaining the formation procedure of a black line. It is an example of the figure supplemented about a black solid pattern and two white lines. It is an example of the figure supplemented about a black solid pattern and two white lines. It is a figure which shows an example of a spot light and a test pattern. It is a figure which shows an example of a spot light and a test pattern. It is an example of the figure explaining the identification method of an edge position. It is a figure which shows an example of the increase rate of an absorption area and an absorption area, respectively. It is an example of the figure explaining the diameter of a spot light, and the line width of a test pattern. It is an example of the figure explaining the diameter of a spot light, and the line width of a test pattern. FIG. 2 is an example of a diagram schematically illustrating a head arrangement and a test pattern of a line type image forming apparatus. It is a figure which respectively shows an example of the absorption area which is an example of the figure which illustrates typically the detection voltage at the time of scanning a test pattern, and the increase rate of an absorption area. It is a figure which shows an example of the reflection intensity when the color of an ink and a sheet material is both yellow. It is a flowchart figure which shows an example of the procedure in which a correction process execution part correct | amends a droplet discharge timing. 1 is an example of a diagram schematically illustrating an image forming system having an image forming apparatus and a server. 2 is a diagram illustrating an example of a hardware configuration diagram of a server and an image forming apparatus. FIG. 1 is an example of a functional block diagram of an image forming system. FIG. 3 is an example of a flowchart illustrating an operation procedure of the image forming system. It is a figure which shows an example of the relationship between a general test pattern and the intensity | strength of reflected light.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is an example of a diagram for explaining an outline of a test pattern forming method of this embodiment. As shown in FIG. 1A, the image forming apparatus first forms a black solid pattern with black ink on a blank sheet material. Next, as shown in FIG. 1B, the image forming apparatus forms two white lines with white ink so as to overlap the black solid pattern. By doing so, three lines of a white line, a black line, and a white line are formed. However, if the sheet material and the white line are not distinguished, one black line is formed.

  As shown in FIG. 1C, when the spot light scans on the pattern, the spot light scans in the order of the white line, black line, and white line, so that the intensity of the reflected light suddenly increases at the boundary between the white line and the black line. To decrease. Therefore, the position of the boundary between the white line and the black line can be detected.

  FIG. 2A is an example of a diagram showing the relationship between the position of the white line and the intensity of the reflected light. The image forming apparatus detects the boundary between the white line and the black line by comparing the intensity of the reflected light with a threshold value. This detection method is exactly the same as the conventional method (when a line center such as black or magenta is formed to specify the line center).

  Incidentally, when two boundaries are detected as shown in FIG. 2A, the conventional image forming apparatus detects the centers of the two boundaries as the line centers of the black lines. However, the purpose of this embodiment is to adjust the discharge timing (discharge position) of white ink.

  Therefore, the image forming apparatus of the present embodiment uses the fact that the black line line center is determined by the positions of the two white lines as shown in FIG. Based on this, the discharge timing of the white ink is corrected. Conventionally, for example, a black line of black ink serving as a reference is formed adjacent to an ink line of a color to be adjusted. This black line is referred to as a reference line in order to distinguish it from a black line formed from a black solid pattern. Conventionally, the discharge timing is adjusted so that the interval between the reference line and the magenta line becomes an ideal value.

  Although the line center of the white line cannot be obtained directly, the edge position on the black line side of the two white lines can be specified. Thereby, the line center of the black line is obtained, and this line center is a value obtained from the edge positions inside the two white lines.

  Therefore, it is only necessary to adjust the discharge timing of the white ink based on the distance between the line centers of the black line and the reference line. When forming two white lines, the image forming apparatus forms white lines using pattern data of white lines in which the distance between the black line and the reference line is the predetermined ideal value L. If there is a misalignment in the position of the white line, the line center of the black line also changes. Therefore, the distance between the line center of the black line and the line center of the reference line deviates from the ideal value L.

  As described above, the image forming apparatus can correct the ejection timing of white ink from the difference between the line center of the black line and the line center of the reference line calculated from the ideal value L and the reflected light. The white ink has a characteristic test pattern formation method, but the ejection timing correction method is exactly the same as the conventional method.

  Therefore, even if a white ink test pattern is formed on a white sheet material, the ejection timing can be adjusted by the same method as in the prior art. When the sheet material and the ink color are the same, the ejection position of the ink of that color can be similarly adjusted by forming a line of the color to be adjusted on the black solid pattern. In the drawing, the white ink is described as an example, but the present invention can be easily applied to inks of other colors having a high reflection intensity.

[Configuration example]
FIG. 3 shows an example of a schematic perspective view of the serial type image forming apparatus 100. The image forming apparatus 100 is supported by the main body frame 70. A guide rod 1 and a width guide 2 are spanned in the longitudinal direction of the image forming apparatus 100, and a carriage 5 is held on the guide rod 1 and the sub guide 2 so as to be able to reciprocate in the arrow A direction (main scanning direction). Yes.

  In the main scanning direction, an endless belt-like timing belt 9 is stretched around a driving pulley 7 and a pressure roller 15, and a part of the timing belt 9 is fixed to the carriage 5. Further, the drive pulley 7 is driven to rotate by the main scanning motor 8, whereby the timing belt 9 moves in the main scanning direction, and the carriage 5 also reciprocates in conjunction with it. The timing belt 9 is tensioned by a pressure roller 15, and the timing belt 9 can drive the carriage 5 without sagging.

  The image forming apparatus 100 also includes a cartridge 60 that supplies ink and a maintenance mechanism 26 that maintains and cleans the recording head.

  The sheet material 150 is intermittently conveyed in the arrow B direction (sub-scanning direction) by a roller (not shown) on the platen 40 below the carriage 5. The sheet material 50 may be a recording medium to which droplets can adhere, such as plain paper such as paper, glossy paper, film, and electronic substrate. The carriage 5 moves in the main scanning direction for each conveyance position of the sheet material 150, and a recording head mounted on the carriage 5 discharges droplets. When the discharge is finished, the sheet material 150 is conveyed again, and the carriage 5 moves in the main scanning direction to discharge the droplets. By repeating this, an image is formed on the entire surface of the sheet material 150, and a printed matter is produced.

  FIG. 4 is an example of a diagram for explaining the operation of the carriage 5 in more detail. The guide rod 1 and the sub guide 2 are stretched between the left side plate 3 and the right side plate 4, and the carriage 5 holds the guide rod 1 and the sub guide 2 slidably by the bearing 12 and the sub guide receiving portion 11. , And can be moved in the directions of arrows X1 and X2 (main scanning direction).

  On the carriage 5, recording heads 21 to 24 for discharging ink of each color are mounted. The ink colors are white (W), black (K), cyan (C), light cyan (LC), magenta (M), light magenta (M), yellow (Y), orange (O), green (G), etc. There is. The range of colors that can be expressed increases as the number of types of white increases, but it is not necessary to mount ink of all colors, and at least black (K), cyan (C), magenta (M), and yellow (Y ) 4 colors are often installed. In the present embodiment, it is assumed that white ink is mounted on these four colors. For example, the recording heads 21 and 22 eject black (K) ink. Only black (K) has two recording heads because black is often used, and one of them can be omitted. The recording head 23 ejects cyan (C) and white (W) ink, and the recording head 24 ejects magenta (M) and yellow (Y) ink.

  As the recording heads 21 to 24, a piezoelectric element is used as a pressure generating means (actuator means) for pressurizing ink in the ink flow path (pressure generating chamber), and a diaphragm that forms the wall surface of the ink flow path is deformed. The so-called piezo type that discharges ink drops by changing the volume in the ink flow path, and discharges ink drops with pressure by heating the ink in the ink flow path using a heating resistor to generate bubbles A so-called thermal type or a diaphragm that forms the wall surface of the ink flow path and an electrode are arranged opposite to each other, and the diaphragm is deformed by an electrostatic force generated between the vibration plate and the electrode, whereby the ink flow path An electrostatic type that discharges ink droplets by changing the internal volume can be used.

  The main scanning mechanism 32 that moves and scans the carriage 5 is disposed on one side in the main scanning direction, the drive pulley 7 that is rotationally driven by the main scanning motor 8, and the other side in the main scanning direction. And a timing belt 9 wound around between the driving pulley 7 and the pressure roller 15. The pressure roller 15 is tensioned outward (in a direction away from the drive pulley 7) by a tension spring (not shown).

  A part of the timing belt 9 is fixedly held by a belt holding unit 10 provided on the back side of the carriage 5, and the carriage 5 is pulled in the main scanning direction as the timing belt 9 moves endlessly.

  Further, an encoder sheet 41 is arranged along the main scanning direction of the carriage 5, and the position of the carriage 5 in the main scanning direction is read by reading the slit of the encoder sheet 42 by the encoder sensor 42 provided on the carriage 5. Can be detected. When the carriage 5 is present in the recording area of the main scanning area, the sheet material 150 is intermittently moved in the arrow Y1 and Y2 directions (sub-scanning direction) perpendicular to the main scanning direction of the carriage 5 by a paper feed mechanism (not shown). Be transported.

  In the image forming apparatus 100 according to the present embodiment described above, the recording heads 21 to 24 are driven according to the image information while moving the carriage 5 in the main scanning direction and intermittently feeding the sheet material 150. By ejecting the droplets, a required image can be formed on the sheet material 150 and a printed matter can be produced.

  On one side surface of the carriage 5, a print position deviation sensor 30 for detecting a deviation in the landing position (reading a test pattern) is mounted. The print position deviation sensor 30 reads a test pattern for detecting the landing position formed on the sheet material 150 by a light receiving element constituted by a light emitting element such as an LED and a reflective photosensor. The print position deviation sensor 30 corresponds to reading means in claims, and the carriage 5 corresponds to relative movement means in claims.

  Since the print position deviation sensor 30 is for the recording head 21, it is preferable to mount another print position deviation sensor 30 in parallel with the recording heads 22 to 24 in order to adjust the droplet discharge timing of the recording heads 22 to 24. . If the carriage 5 is equipped with a mechanism for sliding the print position deviation sensor 30 so as to be in parallel with the recording heads 22 to 24, the single print position deviation sensor 30 can eject droplets from the recording heads 22 to 24. The timing can be adjusted. Alternatively, even when the image forming apparatus 100 sends the sheet material 150 in the reverse direction, the droplet discharge timings of the recording heads 22 to 24 can be adjusted by the single print position deviation sensor 30. In the image forming apparatus 100 according to the present embodiment, after the droplet discharge timing of the recording heads 22 to 24 is adjusted based on the output of the print position deviation sensor, the carriage 5 is moved in the main scanning direction, and the sheet material 150 is moved. While intermittently feeding, the recording heads 21 to 24 are driven according to the image information at the adjusted timing. By ejecting droplets according to this driving, an image without deviation is formed on the sheet material 150, and a printed matter is produced.

  FIG. 5 is an example of a block diagram of the control unit 300 of the image forming apparatus 100. The control unit 300 includes a main control unit 310 and an external I / F 311. The main control unit 310 includes a CPU 301, a ROM 302, a RAM 303, an NVRAM 304, an ASIC 305, and an FPGA (Field Programmable Gate Array) 306. The CPU 301 executes a program 3021 stored in the ROM 302 to control the entire image forming apparatus 100. In addition to this program 3021, the ROM 302 stores fixed data such as initial values and control parameters. The RAM 303 is a working memory that temporarily stores programs, image data, and the like, and the NVRAM 304 is a non-volatile memory that holds data such as setting conditions while the apparatus is powered off. The ASIC 305 performs various signal processing and rearrangement on the image data, and controls various engines. The FPGA 306 processes input / output signals for controlling the entire apparatus.

  The main control unit 310 controls the entire apparatus and controls related to test pattern formation, test pattern detection, landing position adjustment (correction), and the like. As will be described later, in this embodiment, the CPU 301 mainly executes the program 3021 stored in the ROM 302 to detect the edge position. However, part or all of the processing may be performed by an LSI such as the FPGA 306 or the ASIC 305.

  The external I / F 311 is a communication device for communicating with other devices connected to the network, a bus and a bridge for connecting to the USB and IEEE1394, and sends data from the outside to the main control unit 310. The external I / F 311 outputs the data generated by the main control unit 310 to the outside. A removable storage medium 320 can be attached to the external I / F 311, and the program 3021 is distributed in a state stored in the storage medium 320 or via an external communication device.

  The control unit 300 includes a head drive control unit 312, a main scanning drive unit 313, a sub-scanning drive unit 314, a paper feed drive unit 315, a paper discharge drive unit 316, and a scanner control unit 317. The head drive control unit 312 controls the presence / absence of ejection of each of the recording heads 21 to 24, the droplet ejection timing and the ejection amount when ejecting. The head drive control unit 312 has an ASIC for head data generation array conversion for controlling the drive of the recording heads 21 to 24 (head driver), and based on the print data (dot data subjected to dither processing), A drive signal indicating the presence / absence of a droplet and the size of the droplet is generated and supplied to the recording heads 21 to 24. The recording heads 21 to 24 have a switch for each nozzle, and the recording heads 21 to 23 have a size specified at the position of the sheet material 150 specified by the print data by being turned on / off based on a drive signal. Land the droplet. The head driver of the head drive control unit 312 may be provided on the recording heads 21 to 24 side, or the head drive control unit 312 and the recording heads 21 to 24 may be integrated. The illustrated configuration is an example.

  A main scanning drive unit (motor driver) 313 drives a main scanning motor 8 that moves and scans the carriage 5. The main controller 310 is connected to the encoder sensor 42 that detects the carriage position described above, and the main controller 310 detects the position of the carriage 5 in the main scanning direction based on the output signal. Then, the carriage 5 is reciprocated in the main scanning direction by drivingly controlling the main scanning motor 8 via the main scanning driving unit 313.

  A sub-scanning driving unit (motor driver) 314 drives a sub-scanning motor 132 for feeding paper. An output signal (pulse) from the rotary encoder sensor 131 that detects the amount of movement in the sub-scanning direction is input to the main control unit 310, and the main control unit 310 detects the paper feed amount based on this output signal, By driving and controlling the sub-scanning motor 132 through the scanning drive unit 314, the sheet material is fed through a conveyance roller (not shown).

  A paper feed driver 315 drives a paper feed motor 133 that feeds a sheet material from a paper feed tray. The paper discharge driving unit 316 drives a paper discharge motor 134 that drives a roller for discharging the sheet material 150 on which an image is formed onto the platen. The paper discharge drive unit 316 may be substituted by the sub-scanning drive unit 314.

  The scanner control unit 317 controls the image reading unit 135. The image reading unit 135 optically reads a document and generates image data.

  The main control unit 310 is connected to an operation / display unit 136 including various keys such as a numeric keypad and a print start key and various displays. The main control unit 310 receives a key input operated by the user via the operation / display unit 136, displays a menu, and the like.

  Although not shown in the drawings, a recovery drive unit for driving a maintenance recovery motor that drives the maintenance mechanism 26, a solenoid drive unit (driver) for driving various solenoids (SOL), a clutch for driving electromagnetic cracks, etc. You may have a drive part. In addition, detection signals from various other sensors (not shown) are also input to the main control unit 310, but are not shown.

  The main control unit 310 performs a process of forming a test pattern on the sheet material, and performs light emission drive control for causing the light emitting element of the print misregistration sensor 30 mounted on the carriage 5 to emit light with respect to the formed test pattern. Then, the output signal of the light receiving element is acquired, the reflected light of the test pattern is electrically read, the landing position deviation amount is detected from the read result, and the droplet ejection of the recording heads 21 to 24 is further performed based on the landing position deviation amount. Control is performed to correct the timing so that the landing position deviation is eliminated.

[Correction of landing position deviation]
FIG. 6 is an example of a diagram schematically illustrating a configuration for the print position deviation sensor 30 to detect the edge position of the test pattern. FIG. 6 is a view of the recording head 21 and the print position deviation sensor 30 of FIG. 4 as viewed from the right side plate 4.

  The print position deviation sensor 30 has a light emitting element 402 and a light receiving element 403 arranged in a direction orthogonal to the main scanning direction. The arrangement of the light emitting element 402 and the light receiving element 403 may be reversed. The light emitting element 401 projects spot light, which will be described later, onto the test pattern 400, and the light receiving element 403 receives light reflected by the sheet material 150, reflected light from the platen 40, and other scattered light. The light emitting element 402 and the light receiving element 403 are fixed to the inside of the housing, and the surface of the printing position deviation sensor 30 facing the platen 40 is shielded from the outside by a lens 405. As described above, the print position deviation sensor 30 is packaged and can be distributed alone.

  In the print position deviation sensor 30, the light emitting element 402 and the light receiving element 403 are arranged in a direction orthogonal to the scanning direction of the carriage 5 (arranged in parallel in the sub-scanning direction). Thereby, the influence on the detection result by the movement speed fluctuation | variation of the carriage 5 can be reduced.

  The light emitting element 402 is, for example, an LED, and the peak emission wavelength is 563 nano [m] corresponding to green. In addition, the light receiving element 403 has a peak light receiving sensitivity wavelength of 560 nanometers according to the light emitting element. The reason for adopting such a wavelength is that the ink color of a general test pattern is mainly black, magenta, and cyan, but the reflection intensity of both magenta and cyan inks is small (is easily absorbed), This is because the area is around 560 nanometers. On the other hand, the reflection intensity of a color like white is high.

  Further, the spot diameter formed by the light emitting element 402 is in the order of mm in order to use an inexpensive lens without using a highly accurate lens. Although this spot diameter is related to the edge detection accuracy of the test pattern, the edge position can be detected with sufficiently high accuracy even in the mm order if the edge position is obtained in the present embodiment. However, it is possible to make the spot diameter smaller.

  The CPU 301 starts the landing position deviation correction at a predetermined timing. This timing is specified, for example, when the user gives an instruction to correct landing position deviation from the operation / display unit 136, and because the light emitting element 402 emits light before the ink is ejected by the CPU 301, and the intensity of reflected light at that time is less than a predetermined value. The timing at which the sheet material 150 is determined, the temperature and humidity at the time of the last landing position deviation correction are stored, and the timing at which it is determined that either the temperature or the humidity has deviated by more than a threshold value, periodically (every day, Weekly, monthly, etc.).

  The formation of the test pattern will be described. The CPU 301 instructs the main scanning control unit 313 to reciprocate the carriage 5 and the head drive control unit 312 to discharge droplets using a predetermined test pattern as print data. The main scanning control unit 313 causes the carriage 5 to reciprocate in the main scanning direction with respect to the sheet material 150, and the head drive control unit 312 ejects droplets from the recording head 21, so that at least two or more independent members are used. A test pattern including a line is formed. In addition, as a test pattern for ink with a high reflection intensity, pattern data in which a solid pattern with a low reflection intensity and a reference line are alternately formed, and two lines with a color with a high reflection intensity are formed. Pattern data is prepared.

  Further, the CPU 301 performs control for reading the test pattern formed on the sheet material 150 by the print position deviation sensor 30. Specifically, the CPU 301 sets a PWM value for driving the light emitting element 402 of the printing position deviation sensor 30 in the light emission control unit 511, and the output of the light emission control unit 511 is smoothed by the smoothing circuit 512, and the driving circuit. 513. The drive circuit 513 drives the light emitting element 402 to emit light, and the spot light is irradiated from the light emitting element 402 to the test pattern of the sheet material 150. The light emission control unit 511, the smoothing circuit 512, the drive circuit 513, the photoelectric conversion circuit 521, the low-pass filter 522, the A / D conversion circuit 523, and the correction processing execution unit 526 are mounted on the main control unit 310 or the control unit 300. ing. The shared memory 525 is, for example, the RAM 303.

  By irradiating the test pattern on the sheet material with the spot light from the light emitting element 402, the reflected light reflected from the test pattern enters the light receiving element 403. The light receiving element 403 outputs an intensity signal of the reflected light to the photoelectric conversion circuit 521. Specifically, the photoelectric conversion circuit 521 photoelectrically converts the intensity signal and outputs this photoelectric conversion signal to the low-pass filter circuit 522. The low-pass filter circuit 522 outputs a photoelectric conversion signal to the A / D conversion circuit 523 after removing high-frequency noise. The A / D conversion circuit 523 A / D converts the photoelectric conversion signal and outputs the signal to a signal processing circuit (FPGA) 306. The signal processing circuit (FPGA) 306 stores in the shared memory 525 detection voltage data (detection voltage and detection voltage data are used without distinction), which is a digital value of the A / D converted detection voltage. The intensity data storage means in the claims corresponds to, for example, the shared memory 525.

  The correction processing execution unit 526 reads the detection voltage data stored in the shared memory 525, corrects the landing position deviation, and sets it in the head drive control unit 312. That is, the correction processing execution unit 526 calculates the landing position deviation amount by detecting the line center from the edge position of the test pattern and comparing it with the appropriate distance between the two lines. The correction processing execution unit 526 corresponds to a position detection unit in the claims.

  The correction processing execution unit 526 calculates a correction value of the droplet discharge timing when driving the recording head 21 so that the landing position deviation is eliminated, and sends the calculated correction value of the droplet discharge timing to the head drive control unit 312. Set. Accordingly, when the recording head 21 is driven, the head driving control unit 312 corrects the droplet discharge timing based on the correction value and then drives the recording head 21, thereby reducing the landing position deviation of the droplet. be able to.

  FIG. 7 is an example of a functional block diagram of the correction process execution unit 526. The correction process execution unit 526 includes a test pattern formation unit 617, an ejection timing correction unit 616, and a pattern data storage unit 618.

  The pattern data storage unit 618 stores pattern data of a test pattern for each color ink. For example, when correcting the ejection timing of ink of other colors with reference to black, the pattern data includes black and other color inks (for example, magenta) with low reflection intensity, as shown in FIG. The reference lines are alternately formed at a fixed distance. The pattern data (test pattern) of ink having a high reflection intensity will be described later. The pattern data storage unit 618 corresponds to pattern data storage means in the claims.

  The test pattern forming unit 617 forms a test pattern for each color (for each of the recording heads 21 to 24) on the sheet material. The test pattern forming unit 617 corresponds to the test pattern forming means in the claims. The ejection timing correction unit 616 corrects the droplet ejection timing based on the landing position deviation amount obtained from the edge position of the test pattern.

[Test pattern of color ink with high reflection intensity]
FIG. 8 is an example of a diagram for explaining a test pattern of the present embodiment. FIG. 8 shows a line of ink having a low reflection intensity (white in the figure), a solid pattern of ink having a low reflection intensity (black in the figure), and a line of ink having a high reflection intensity compared to the conventional test pattern. It shows that the ink line is replaced with a low reflection intensity.

  The test pattern of the present embodiment is obtained by replacing the white line with the black line in the enlarged view when the reference line and the white line are alternately formed with black as the reference line. Since the width of the white line is D, the width of the black line is also D, but the width of the black line is not necessarily D. The width D of the black line is defined by the positions of the two left and right white lines formed so as to overlap the black solid pattern.

FIG. 9 is an example of a diagram illustrating a black line forming procedure. The test pattern for adjusting the discharge timing of the white ink includes the following patterns.
(i) Pattern in which black reference lines and black solid patterns are alternately formed
(ii) Two White Line Patterns Overlaid on a Black Solid Pattern As shown in FIG. 9A, the test pattern forming unit 617 alternately forms a black reference line and a black solid pattern. . The width of the black solid pattern is larger than the black reference line, narrower than the interval between the two reference lines, and wider than the interval between the inner edges of the two white lines. Note that the width D of the black reference line is larger than the spot diameter of the spot light. As for the width of the black solid line, it is preferable that the width of the black solid line is narrow because the consumption of black and white inks is small if the width is narrow within the range satisfying this condition. On the other hand, the width of the black solid pattern is a value that takes into account the amount of misalignment of the white line (for example, the edge of the black solid pattern must be under the white line, Align the edge position).

  As shown in FIG. 9B, the test pattern forming unit 617 forms two white lines that overlap so that a black line with a width D remains on the black solid pattern. The positions of the left and right edges of the black line are determined by the two white lines. One or more of the two white lines may be formed by a plurality of white lines. That is, if the right and left sides of the black solid pattern are covered with white ink, the white ink may be ejected in several steps.

  The white line is formed so that the distance between the line center of the black line and the line center of the adjacent reference line has a predetermined ideal value L. The interval of the ideal value L is provided for the reference pattern on the left side of the black line and the reference pattern on the right side. Since the reference line and the black solid pattern are alternately formed, the distance between the line center of the reference line and the line center of the black line is always equal to the ideal value L. However, it does not have to be equally spaced, and it is sufficient that the ideal value L between the line center of the reference line and the line center of the black line is known.

  Since the line center of the reference line changes, the white line should not cover the reference line (the white line should not overlap with the reference line). Therefore, the width of the white line starts from the position D / 2 from the center of the solid black pattern, and the width is less than “LD” at the maximum. The shape of the white line on the reference line side may not be a straight line. In this case, the white line is not called a "line", but the function is not changed.

10 and 11 are examples of diagrams supplementing the black solid pattern and the two white lines. The black solid pattern and the two white lines have the following properties.
A. As described above, the distance between the line center of the black line and the line center of the reference line is a known ideal value L. As shown in FIG. 10A, if the distance from the line center of the black line to the left and right reference lines is equal to L, the lines need not be distinguished.
B. If the width of the reference line is D, the width of the black line may not be D (because the line center need only be known for the black line and the reference line). For this reason, as shown in FIG. 10B, the width of the black line may be less than D or larger than D as shown in FIG. The black line width D and the line center are determined by the position of the white line. The minimum width of the black line (defined by the edge position of the white line) is preferably equal to or greater than the spot diameter d of the spot light.
C. Of the solid black pattern, the portion covered by the white line (the portion where the width is at least the spot diameter d) may be formed in any manner as long as it does not reach the reference line. For example, as shown in FIG. 11A, the width of the black solid pattern may be increased so that the white line overlaps the black solid pattern within a sufficient range. Also. As shown in FIG. 11B, the width of the black solid pattern may be formed to be slightly larger than the spot diameter d so that the white line overlaps with the black solid pattern in a minimum range. In addition, as shown in FIG. 11C, if the spot diameter is d / 2 or more on the left and right with respect to the line center of the black line, the black solid pattern is unequal on the left and right with respect to the line center of the black line. It may be a length.
D. As shown in FIGS. 11A to 11C, the edge positions inside the left and right white lines are defined such that the distance between them is the width D. Further, the outer edge positions of the left and right white lines are defined to be outside the edge positions of the black solid pattern (the side far from the line center of the black line).

  From the viewpoint of ink consumption, as shown in FIG. 11D, the width of the black solid pattern is set to a minimum larger than D, for example, and the width of white ink is larger than D of the black solid pattern. The minimum width that can be filled is preferable.

[Spot light position and edge position]
Next, the relationship between the spot light and the edge position will be described with reference to FIGS.
FIG. 12 is a diagram illustrating an example of spot light and a test pattern. The spot light moves so as to cross a plurality of lines (one line in the figure) constituting the test pattern at a constant speed (constant speed). The speed of crossing may be variable, but is constant during the crossing. Since the sheet material such as paper is moved in the longitudinal direction of the line by paper feeding, the spot light moves diagonally across the line, but the edge position specifying method is the same even if the sheet material stops. . In the spot light of a general wavelength and the sheet material, the reflected light of the spot light may decrease as the overlapping area of the test pattern increases.

  In FIGS. 12 and 13, the spot diameter d = the line width L of the test pattern. Actually, the spot light becomes a slight ellipse, but since the ellipse has a long axis parallel to the test pattern, the shape of the spot light hardly affects the accuracy of the edge position.

FIG. 13 is an example of a diagram illustrating a specific outline of the edge position according to the present embodiment. Numbers I to V in FIG. 13A indicate the passage of time, and the lower the spotlight, the longer the passage of time.
Time I: Spot light and test pattern do not overlap.
Time II: Half of the spot light is superimposed on the test pattern. At this moment, the reduction rate of the reflected light becomes the largest (the overlapped area changes most positively in unit time).
Time III: The entire spot light is superimposed on the test pattern. At this moment, the intensity of the reflected light becomes the smallest.
Time IV: Half of the spot light is superimposed on the test pattern. At this moment, the increase rate of the reflected light becomes the largest (the overlapping area changes most negatively per unit time).
Time V: The spot light passes through the test pattern, and the spot light and the test pattern do not overlap.

  It is time II and IV that the center of gravity of the spot light coincides with the edge position of the line of the test pattern. Therefore, if it can be detected from the reflected light that the spot light and the line have the relationship between the times II and IV, the edge position can be specified with high accuracy.

  13B shows an example of the detection voltage of the light receiving element, FIG. 13C shows an example of the absorption area (the overlapping area of the spot light and the test pattern), and FIG. 13D shows the absorption of FIG. 13C. An example of the increase rate of the absorption area obtained by differentiating the area is shown. In FIG. 13 (d), equivalent information can be obtained by differentiating the output waveform of FIG. 13 (b). Further, although the absorption area is calculated from the detection voltage, for example, it does not have to be an absolute value. Therefore, the absorption area in FIG. 13C is obtained by subtracting the detection voltage in FIG. 13B from the predetermined value. A waveform similar to is obtained.

  As described above, the decrease rate of the reflected light becomes the largest at time II (the overlapping area changes most positively in unit time), and the increase rate of the reflected light becomes the largest at time IV (superimposition). Area changes most negatively per unit time). As shown in FIG. 13 (d), the point at which the increase rate changes from an increasing trend to a decreasing trend is coincident with time II, and the point at which the increase rate changes from a decreasing trend to an increasing trend is at time IV. Is consistent with

  A point that changes from an increasing tendency to a decreasing tendency or vice versa is a point where the bending direction changes in a curved line on a plane, that is, an inflection point. From the above, if the output signal indicates an inflection point, the spot light coincides with the edge position of the test pattern. Therefore, if the inflection point is detected with high accuracy, the edge position can also be specified with high accuracy.

[Identification of edge position]
FIG. 14 is an example of a diagram illustrating a method for specifying an edge position. FIG. 14A shows a schematic diagram of the detection voltage, and FIG. 14B shows an enlarged view of the detection voltage. The approximate value of the inflection point can be obtained experimentally by the correction processing execution unit 526 or the developer. As described above, for example, the inflection point is a position where the detected voltage and the absorption area are differentiated and the inclination is closest to zero.

  The upper limit threshold value Vru and the lower limit threshold value Vrd of the detection voltage are determined in advance so that this inflection point is included. As will be described later, the CPU 301 calibrates the output of the light emitting element 402 and the sensitivity of the light receiving element 403 so that the detection voltage becomes substantially the same constant value (4 [V] described later) in an area where there is no test pattern. By correcting the drawing density according to the present embodiment, the maximum value of the detection voltage can be set to substantially the same constant value, so that an inflection point is included between the upper limit threshold value Vru and the lower limit threshold value Vrd.

  The discharge timing correction unit 616 searches for the falling portion of the detected voltage in the direction indicated by the arrow Q1, and stores the point where the detected voltage is equal to or lower than the lower limit threshold Vrd as the point P2. Next, the point P2 is searched in the direction of the arrow Q2, and the point where the detected voltage exceeds the upper limit threshold value Vru is stored as the point P1.

  Then, a regression line L1 is calculated using a plurality of detection voltage data between the points P1 and P2, and an intersection point between the regression line L1 and the upper and lower threshold intermediate value Vc is calculated as an intersection point C1.

  Similarly, the discharge timing correction unit 616 searches the rising portion of the detected voltage in the direction indicated by the arrow Q3, and stores the point where the detected voltage is equal to or higher than the lower limit threshold Vru as the point P4. Next, a search is made from the point P4 in the direction indicated by the arrow Q4, and the point where the detected voltage is equal to or lower than the upper threshold value Vrd is stored as the point P3.

  Then, a regression line L2 is calculated using a plurality of detected voltage data between the points P3 and P4, and an intersection point between the regression line L2 and the intermediate value Vc of the upper and lower thresholds is calculated as an intersection point C2. Since the intersection C1 and the intersection C2 are edge positions of one line, the center of the intersections C1 and C2 is a line center (line position).

  Thereafter, the ejection timing correction unit 616 obtains the line centers of a plurality of lines, and calculates the difference between the ideal distance L (= ideal value L) between the two lines of the test pattern and the distance between the line centers. calculate. Since this difference is a deviation of the actual line position from the ideal line position, it becomes the landing position deviation amount. The discharge timing correction unit 616 calculates a correction value for correcting the timing (droplet discharge timing) for discharging a droplet from the recording head 21 based on the calculated landing position deviation amount, and uses the correction value as the head drive control unit 312. Set to. As a result, the head drive control unit 312 drives the recording head 21 at the corrected droplet discharge timing, so that the amount of landing position deviation is reduced.

[Cause of reduced accuracy]
As described above, when an edge is detected using detection voltage data between the upper threshold and the lower threshold, the edge cannot be detected unless at least an inflection point is included between the upper threshold and the lower threshold. The width formed by the upper threshold and the lower threshold (two thresholds) is hereinafter referred to as a “threshold region”. The threshold region is based on the detection voltage, but can also be defined by the absorption area corresponding to the detection voltage.

  FIG. 15 is a diagram illustrating an example of an absorption area and an increase rate of the absorption area. If there is an inflection point in the threshold area A of FIG. 15, the ejection timing correction unit 616 can detect the edge position with high accuracy as described in FIG.

  On the other hand, if there is an inflection point in the threshold area B of FIG. 15, the ejection timing correction unit 616 cannot detect an accurate edge position even if a regression line is obtained from the A threshold area. Further, if it is known that the inflection point is in the B threshold area, the discharge timing correction unit 616 can obtain the regression line by moving the threshold area from A to B. If the position is greatly shifted, there is a possibility that the curve of the detection voltage or the absorption area is deformed. For example, if the discharge timing correction unit 616 obtains a regression line from a threshold region where the slope of the curve has increased, the intersections C1 and C2 may also be greatly shifted. In the lower diagram of FIG. 11, the width of the position including the vicinity of the apex can be estimated in a sufficiently narrow range in the threshold area of A, whereas the inflection point (in the threshold area B in FIG. 15) is estimated in the threshold area of B. This is indicated by the fact that the width of the position including the vicinity is difficult to estimate in a narrow range.

  Therefore, when the amplitude of the detected voltage fluctuates so that the inflection point does not enter the threshold area A, the edge position is specified from the threshold area A, or the inflection point itself is obtained and the threshold area is moved to move the edge position. It can be seen that determining is not preferred.

[Spot light diameter and test pattern line width]
In FIG. 13, the spot diameter d = the line width L of the test pattern, but the edge position can be detected even if “spot diameter d> the test pattern line width L” or “spot diameter d <the test pattern line width L”. It is.

  FIG. 16A shows an example of spot light and a test pattern in a relationship of spot diameter d> line width L of the test pattern. Here, it is assumed that “d / 2 <L <d”. FIG. 16B shows an example of the detection voltage of the light receiving element, FIG. 16C shows an example of the absorption area, and FIG. 16D shows the increase rate of the absorption area obtained by differentiating the absorption area of FIG. An example is shown respectively.

  Since the spot diameter d> the line width L of the test pattern means that the spot light and the test pattern do not completely overlap, as is apparent from the increase rate of the absorption area in FIG. When the right edge of the light passes the test pattern, the absorption area starts to decrease, and the increase rate decreases rapidly.

  However, in the present embodiment, if the detection voltage data near the inflection point is obtained, the intersections C1 and C2 can be obtained, so the diameter d of the spot light only needs to be d / 2 <L. That is, it is sufficient that the spot diameter d 1 is not extremely larger than the line width L of the test pattern.

  FIG. 17A shows an example of the spot light and the test pattern in the relationship of spot diameter d <line width L of the test pattern. FIG. 17B shows an example of the detection voltage of the light receiving element, FIG. 17C shows an example of the absorption area, and FIG. 17D shows the increase rate of the absorption area obtained by differentiating the absorption area of FIG. An example is shown respectively.

  Since the spot diameter d <the line width L of the test pattern means that the state in which the spot light and the test pattern are completely superimposed continues, as shown in FIGS. A region having a constant absorption area is generated. Moreover, as shown in FIG.17 (d), the area | region where the increase rate of an absorption area becomes zero arises. After that, when the right end of the spot light gets over the test pattern, the absorption area starts to decrease, and the increase rate gradually decreases (the decrease rate increases).

  In such a case, as in FIG. 13, the detection voltage data near the inflection point is sufficiently obtained, so that the ejection timing correction unit 616 can sufficiently obtain the intersection points C1 and C2.

[In the case of a line type image forming apparatus]
In this embodiment, the serial type image forming apparatus 100 of FIGS. 3 and 4 has been described as an example. However, the line type image forming apparatus 100 can also correct the landing position deviation amount by the same method. The line type image forming apparatus 100 will be briefly described.

  FIG. 18 is an example of a diagram schematically illustrating the head arrangement and the test pattern of the line type image forming apparatus 100. The head fixing bracket 160 is fixed so as to be spanned from end to end in the main scanning direction orthogonal to the sheet material conveyance direction. In the head fixing bracket 160, recording heads 180 of black, cyan, white, magenta, and yellow ink are arranged from the upstream side over the entire area in the main scanning direction. The recording heads 180 for each color are arranged in a staggered manner so that the ends overlap. By doing so, droplets with sufficient resolution are ejected even at the end of the recording head 180, so that it is not necessary to dispose one recording head 180 over the entire region in the main scanning direction, and an increase in cost can be suppressed. Note that one recording head 180 may be arranged in the entire region in the main scanning direction for each ink color, or the overlapping region in the main scanning direction of the recording head 180 for each color may be made longer.

  Downstream of the head fixing bracket 160, a sensor fixing bracket 170 is fixed so as to be spanned from end to end in the main scanning direction orthogonal to the sheet material conveyance direction. The sensor fixing bracket 170 has as many print position deviation sensors 30 as the number of heads. That is, one print position deviation sensor 30 is arranged so as to at least partially overlap one print head 180 in the main scanning direction. Further, one printing position deviation sensor 30 has a pair of light emitting element 402 and light receiving element 403. The light emitting element 402 and the light receiving element 403 are arranged in parallel substantially in the main scanning direction.

  The image forming apparatus 100 having such a form forms each line constituting the test pattern so that the longitudinal direction of the line is parallel to the main scanning direction. When correcting the landing position deviation of the droplets of other colors with reference to black, the image forming apparatus 100 may include a black reference line and a black solid pattern and two white lines, a black line and a magenta line, or A black line and a cyan line are formed. Then, similarly to the serial type image forming apparatus 100, the edge position of the black line is detected, and the droplet discharge timing is corrected based on the positional deviation amount. In the image forming apparatus 100 of FIG. 18, the paper feed mechanism (for example, the sub-scanning motor 132) corresponds to the relative movement means in the claims.

  As described above, also in the line type image forming apparatus 100, the landing position deviation can be corrected by appropriately arranging the print position deviation sensor 30.

[Example of detection voltage]
FIG. 19 is an example of a diagram schematically illustrating the detection voltage when the test pattern of the present embodiment is scanned. As described so far, the reference lines and the black lines are alternately formed, and three black lines in total, that is, a total of six black lines are formed at equal intervals of the ideal value L.

  The detection voltage obtained when the spot light scans the test pattern rapidly decreases between the reference line and the black line. That is, the black line suddenly starts decreasing at the left edge and suddenly increases at the right edge. Therefore, in an ideal case, the interval between the minimum portions is equal to L.

  The left edge position of the black line defines the right edge position of the white line, and the right edge position of the black line defines the left edge position of the white line. Therefore, if the white line is formed at an ideal position, the distance between the line center of the reference line and the line center of the black line is L.

  However, since the line center of the black line is defined by the edge positions of the two white lines, for example, if the discharge position of the white ink tends to shift to the right, the line center of the black line also shifts to the right. Therefore, it can be understood that the discharge timing of the white ink can be adjusted based on the difference between the line center of the reference line and the line center of the black line and the ideal value L. This adjustment method is exactly the same as magenta, cyan, etc. that adjust the discharge timing with reference to the reference line, and the white ink discharge timing adjustment is based on the conventional algorithm (method for calculating the adjustment amount of the discharge timing) ) Can be adjusted with the exact same algorithm.

[About inks other than white]
White ink is only an example of ink having high reflection intensity, and the ejection timing adjustment method of the present embodiment can be similarly applied to inks of other colors having high reflection intensity. For example, it can be suitably applied to glossy inks such as gold, silver and enamel. A criterion for ink having a high reflection intensity is that the inflection point of the detection voltage does not fall below the upper limit threshold Vud with respect to the peak wavelength of the light emitting element 402. Therefore, it cannot be applied only to a certain color (for example, JIS Z 8102: 2001), but if the ejection timing cannot be adjusted by the conventional method, the adjustment method of this embodiment may be applied.

  The ink has an attribute of transparency in addition to the color, but the ink of the present embodiment needs to have a low transmittance so that a black solid pattern is not detected.

  However, when the test pattern forming unit 617 discharges the transparent ink in such a manner that the transparency is negligible, the discharge timing may be adjusted.

  Further, in the present embodiment, the sheet material and the ink color are the same or similar, but it is not necessary to be completely the same. For example, if the Euclidean distance in any color space of two colors measured by a colorimeter is within a predetermined value, it can be regarded as the same color.

In this embodiment, the white ink and the white sheet material are taken as an example. However, the present invention can be similarly applied to a case where both the ink and the sheet material are yellow.
FIG. 20A is a diagram illustrating an example of the reflection intensity when the ink and the sheet material are both yellow. As in the case of white ink, the line center of the black line is defined by the edge position of the two yellow lines on the black line side. When the spot light scans the test pattern, the detection voltage falls below the lower limit threshold value Vrd for the reference line and the black line, and exceeds the upper limit threshold value Vru for the yellow line and the sheet material (the inflection point enters the threshold area). Therefore, the discharge timing of yellow ink can be adjusted in the same manner as white ink.

On the other hand, when the color of the sheet material and the ink is relatively low and the reflection intensity is low, it may be difficult to adjust the ejection timing like the white ink.
FIG. 20B is a diagram illustrating an example of the reflection intensity when the ink and the sheet material are both cyan. The detection voltage is lower than the lower limit threshold value Vrd for the reference line and the black line, but the cyan line and the sheet material may not exceed the upper limit threshold value Vru. Therefore, the test pattern of this embodiment can be applied when the detection voltage of the color of the ink and the sheet material exceeds the upper limit threshold value Vru.

  Further, the color of the black solid pattern does not need to be black, and may be a color having a reflection intensity such that the detection voltage exceeds the upper limit threshold Vru (the inflection point enters the threshold region). The reference line is also often formed in black, but the reference line does not need to be black, and if the color has a reflection intensity such that the detection voltage exceeds the upper threshold Vru (the inflection point enters the threshold region). Good.

[Operation procedure]
FIG. 21A is a flowchart illustrating an example of a procedure in which the correction processing execution unit 526 corrects the droplet discharge timing.

  First, the CPU 301 instructs the main control unit 310 to start landing position deviation correction. In response to this instruction, the main control unit 310 drives the sub-scanning motor 132 via the sub-scanning driving unit 314 to convey the sheet material 150 to just below the recording head 21 (S1).

  Next, the main control unit 310 drives the main scanning motor 27 via the main scanning drive unit 313 to move the carriage 5 onto the sheet material 150 and receive light from the light emitting element at a specific location on the sheet material 150. The element is calibrated (S2).

  FIG. 21B is an example of a flowchart for explaining the process of S2. The calibration is a process of adjusting the light amount of the light emitting element so that the detection voltage of the light emitting element is adjusted within a desired range (for example, adjusted within a range of 4V ± 0.4 [V]).

  The CPU 301 sets a PWM value for driving the light emitting element 402 of the print position deviation sensor 30 in the light emission control means 511, smoothes it by the smoothing circuit 512, and then gives it to the driving circuit 513, whereby the driving circuit 513 The light emitting element 402 is driven to emit light (S21).

  The intensity signal detected by the light receiving element 403 of the print position misalignment sensor 30 is stored in the shared memory 525, and the CPU 301 checks whether or not it has a desired voltage value (S22).

  If the desired voltage value is reached (OK at S22), the process of FIG. 22B ends. If the desired voltage value is not reached (No in S22), the CPU 301 changes the PWM value (S23) to readjust the light amount.

  Returning to FIG. 21A, the main control unit 310 moves the carriage 5 via the main scanning drive motor 27 without moving the paper while keeping the sub-scanning position of the sheet material 150 as it is. Then, the test pattern forming unit 617 requests the head drive control unit 312 to form a test pattern. The head drive control unit 31 drives the recording heads 22 and 23 using the pattern data stored in the pattern data storage unit 618 (S3). That is, after forming a reference line and a solid black pattern, two white lines are formed to form a white ink test pattern.

  Further, the printing position deviation sensor 30 scans the test pattern with spot light and generates detection voltage data (S4).

  Then, the ejection timing correction unit 616 detects the edge position of the test pattern from the detected voltage data, and corrects the landing position deviation of the droplet (S12). In other words, the ejection timing correction unit 616 calculates the landing position deviation amount by comparing the distance between the line center of the reference line and the line center of the black line with the ideal value L, and the white ink liquid so as to eliminate the landing position deviation. A correction value for the droplet discharge timing is calculated and set in the head drive controller 312.

  As described above, the image forming apparatus according to the present exemplary embodiment is exactly the same as an ink having a low reflection intensity by forming an ink having a high reflection intensity such as white ink so as to define the position of the black line. Thus, the discharge timing can be adjusted.

  In this embodiment, a description will be given of an image forming system in which a correction value of a droplet discharge timing is calculated by a server rather than an image forming apparatus.

  FIG. 22 is an example of a diagram schematically illustrating an image forming system 500 including the image forming apparatus 100 and the server 200. 22, the same parts as those in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted. The image forming apparatus and the server 200 are connected via a network 201. The network 201 is an in-house LAN, a WAN connecting the LANs, the Internet, or a combination of these.

  In the image forming system 500 as shown in FIG. 22, the image forming apparatus 100 forms a test pattern and scans the test pattern with the print position deviation sensor, and the server 200 calculates a correction value of the droplet discharge timing. Accordingly, the processing load on the image forming apparatus 100 can be reduced, and the function for calculating the correction value of the droplet discharge timing can be integrated in the server 200.

  FIG. 23 is a diagram illustrating an example of a hardware configuration diagram of the server 200 and the image forming apparatus 100. The server 200 includes a CPU 51, a ROM 52, a RAM 53, a storage medium mounting unit 54, a communication device 55, an input device 56, and a storage device 57 that are mutually connected by a bus. The CPU 51 reads an OS (Operating System) and a program 570 from the storage device 57, and executes them using the RAM 53 as a working memory. This program performs the following processing.

  The RAM 53 is a working memory (main storage memory) for temporarily storing necessary data, and the ROM 52 stores BIOS, initially set data, a bootstrap rotor, and the like. The storage medium mounting unit 54 is an interface for mounting a portable storage medium 320.

  The communication device 55 is called a LAN card or an Ethernet (registered trademark) card, and is connected to the network 201 to communicate with the external I / F 311 of the image forming apparatus 100. Note that at least the IP address or domain name of the server 200 is registered in the image forming apparatus 100.

  The input device 56 is a user interface that accepts various user operation instructions such as a keyboard and a mouse. A touch panel or a voice input device can be used as the input device.

  The storage device 57 has a nonvolatile memory such as an HDD (Hard Disk Drive) or a flash memory as an entity, and stores an OS, a program, and the like. The program 570 is distributed in a state recorded in the storage medium 320 or downloaded from the server 200 (not shown).

  FIG. 24 is an example of a functional block diagram of the image forming system 500. The correction processing execution unit 526 of the image forming apparatus 100 includes a data transmission unit 621, a data reception unit 622, a test pattern formation unit 617, and a test pattern storage unit 618. Further, the server side has a correction processing calculation unit 620.

  The data transmission unit 621 transmits the detection voltage data stored in the shared memory 525 to the server. The data receiving unit 622 receives the correction value of the droplet discharge timing from the server and sends it to the head drive control unit 312.

  In the figure, the shared memory 525 is included in the image forming apparatus. However, the server 200 may include the shared memory 525, and both the server 200 and the image forming apparatus 100 may include the shared memory 525. Further, the test pattern storage unit 618 may be on the server side, and the image forming apparatus 100 may download it from the server 200 or a server (not shown).

  The server correction processing calculation unit 620 includes a discharge timing correction unit 616. Since the function of the ejection timing correction unit 616 is the same as that of the first embodiment, description thereof is omitted.

  In the image forming system 500, the detection voltage data on the image forming apparatus side is transmitted to the server 200. Since the correction processing calculation unit 620 on the server side calculates a correction value of the ejection timing and transmits it to the image forming apparatus 100, the head drive control unit 312 can change the ejection timing.

  FIG. 25 is an example of a flowchart illustrating an operation procedure of the image forming system 500. As shown in the figure, the server 200 corrects the landing position deviation. The image forming apparatus 100 performs other test pattern formation and scanning voltage generation to generate detection voltage data.

  When the image forming apparatus 100 scans the test pattern and generates detection voltage data (S4), the data transmission unit 621 transmits the detection voltage data to the server (S5).

  Thereafter, when the server calculates the correction value of the droplet discharge timing, the data receiving unit 622 receives the correction value of the droplet discharge timing (S6).

  The server side receives the detected voltage data transmitted from the image forming apparatus (S11). When the detection voltage data is received, the ejection timing correction unit 616 of the server 200 corrects the landing position deviation (S12).

  The server transmits the correction value of the droplet discharge timing to the image forming apparatus (S13).

  As described above, the image forming system 500 can correct the liquid ejection timing of ink such as white having a high reflection intensity with high accuracy, just like the first embodiment, only by changing the place where the processing is performed.

DESCRIPTION OF SYMBOLS 1 Guide rod 2 Sub guide 5 Carriage 7 Drive pulley 8 Main scanning motor 9 Timing belt 21-24 Recording head 30 Print position shift sensor 41 Encoder sheet 42 Encoder sensor 100 Image forming apparatus 200 Server 301 CPU
310 Main Control Unit 312 Head Drive Control Unit 313 Main Scan Drive Unit 314 Sub Scan Drive Unit 402 Light Emitting Element 403 Light Receiving Element 500 Image Forming System 525 Shared Memory 526 Correction Processing Execution Unit 616 Ejection Timing Correction Unit 617 Test Pattern Formation Unit 618 Pattern Data Storage unit 620 Correction processing calculation unit

JP 2001-129980 A JP 2008-229915 A

Claims (10)

An image forming apparatus that reads a test pattern composed of a plurality of lines formed on a recording medium and adjusts ink ejection timing,
A reading means having a light emitting means for irradiating the recording medium with light and a light receiving means for receiving reflected light from the recording medium;
Pattern data storage means for storing pattern data for forming the test pattern;
First pattern data having a solid pattern and a reference line of the first ink having a reflection intensity equal to or lower than the first threshold, and a second pattern having two lines of the second ink having a reflection intensity equal to or higher than the second threshold. Test pattern forming means for reading pattern data of 2 and forming a test pattern;
Relative moving means for moving the recording medium or the reading means at a relatively constant speed;
Intensity data storage means for storing intensity data of the reflected light received by the light receiving means from the scanning position of the light while the light is moving on the test pattern;
Position detecting means for performing a line position determination calculation on the intensity data included within a lower limit from a predetermined upper limit, and detecting the position of the line,
The test pattern forming means includes:
After forming the solid pattern and the reference line based on the first pattern data, a single molding line is formed by being formed on the edge of the solid pattern, and the line center of the reference line and the molding line An image forming apparatus, wherein the two lines are formed so that a distance from the line center is a predetermined distance. The position detecting means detects a line center of the molding line from an interval between two boundaries of the two lines with respect to a center side of the molding line;
2. A discharge position correcting unit that corrects the discharge position of the second ink by comparing an interval between a line center of a reference line and a line center of the molding line with a specified value. The image forming apparatus described.   3. The image forming apparatus according to claim 1, wherein the distance between the line center of the molding line and the line centers of the left and right reference lines is equal.   4. The image forming apparatus according to claim 1, wherein the color of the second ink and the color of the recording medium have a Euclidean distance within a threshold in a predetermined color space. 5.   5. The image forming apparatus according to claim 1, wherein the magnitude of the intensity data of the reflected light received by the light receiving unit from the forming unit of the two lines is equal to or greater than a threshold value. . The magnitude of the intensity data of the reflected light received from the recording medium by the light receiving means is greater than or equal to a threshold value.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein the color of the second ink is substantially white, gold, or silver. A reading means having a light emitting means for irradiating the recording medium with light and a light receiving means for receiving the reflected light from the recording medium;
And a pattern data storage unit for forming a test pattern composed of a plurality of lines, and reading the test patterns of the plurality of lines formed on the recording medium to adjust the droplet discharge timing. A pattern position detection method comprising:
The test pattern forming means includes a first pattern data having a first ink solid pattern having a reflection intensity equal to or lower than the first threshold and a reference line, and 2 of the second ink having a reflection intensity equal to or higher than the second threshold. Reading second pattern data having two lines to form a test pattern;
A relative moving means moving the recording medium or the reading means at a relatively constant speed;
Storing the intensity data of the reflected light received from the scanning position of the light in the intensity data storage means while the light is moving on the test pattern;
A position detecting means, performing a line position determination operation on the intensity data included within a lower limit from a predetermined upper limit, and detecting the position of the line,
The test pattern forming means includes:
After forming the solid pattern and the reference line based on the first pattern data, a single molding line is formed by being formed on the edge of the solid pattern, and the line center of the reference line and the molding line Forming the two lines so that the distance from the line center is a predetermined distance;
And a pattern position detecting method. An image forming system that reads a test pattern formed by discharging droplets on a recording medium and adjusts the discharge timing of the droplets,
A reading means having a light emitting means for irradiating the recording medium with light and a light receiving means for receiving reflected light from the recording medium;
Test pattern forming means for forming a test pattern;
Relative moving means for moving the recording medium or the reading means at a relatively constant speed;
An image forming apparatus having
Intensity data storage means for storing intensity data of the reflected light received by the light receiving means from the scanning position of the light while the light is moving through the test pattern;
First pattern data having a solid pattern and a reference line of the first ink having a reflection intensity equal to or lower than the first threshold, and a first pattern data having two lines of the second ink having a reflection intensity equal to or higher than the second threshold. Test pattern forming means for reading pattern data of 2 and forming a test pattern;
Position detecting means for performing a line position determination calculation on the intensity data included within a lower limit from a predetermined upper limit, and detecting the position of the line,
The test pattern forming means includes:
After forming the solid pattern and the reference line based on the first pattern data, a single molding line is formed by being formed on the edge of the solid pattern, and the line center of the reference line and the molding line The image forming system, wherein the two lines are formed such that a distance from the line center is a predetermined distance. A reading means having a light emitting means for irradiating the recording medium with light and a light receiving means for receiving the reflected light from the recording medium;
A pattern data storage unit for storing pattern data for forming a test pattern composed of a plurality of lines, and using an image forming apparatus having a plurality of lines to read a test pattern of a plurality of lines formed on the recording medium In a method of producing printed matter by adjusting the discharge timing and discharging droplets at the adjusted discharge timing,
The test pattern forming means includes a first pattern data having a first ink solid pattern having a reflection intensity equal to or lower than a first threshold and a reference line, and 2 of the second ink having a reflection intensity equal to or higher than a second threshold. Reading second pattern data having two lines to form a test pattern;
A relative moving means moving the recording medium or the reading means at a relatively constant speed;
Storing the intensity data of the reflected light received from the scanning position of the light in the intensity data storage means while the light is moving on the test pattern;
A position detecting means, performing a line position determination operation on the intensity data included within a lower limit from a predetermined upper limit, and detecting the position of the line,
Correct the discharge timing based on the detected line position,
The test pattern forming means includes:
After forming the solid pattern and the reference line based on the first pattern data, a single molding line is formed by being formed on the edge of the solid pattern, and the line center of the reference line and the molding line A method for producing printed matter, characterized in that the two lines are formed so that the distance from the line center is a predetermined distance.

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