JP2021120191A - Recording device - Google Patents

Abstract

To suppress a color shift on a recording device which has a color shift correcting function and has a color shift when corrected with a read value which is not normal, by determining a color shift, which may be caused as normal corrections are not made because of the read value which is not normal, from a linear LUT for color shift correction, and reporting a determination result to a user to prompt the user to make adjustments again.SOLUTION: A variation amount of a linear LUT for color shift correction is compared with a threshold, and whether corrections based upon normal read values are made is determined and reported to a user.SELECTED DRAWING: Figure 11

Description

The present invention relates to a recording device and a color shift correction method, and more particularly to a method of reducing an influence on correction due to a defect at the time of color shift detection or an operation error.

Conventionally, as one of the output devices for recording an image on various recording media such as paper, a nozzle row having a plurality of recording heads or a plurality of ejection ports (hereinafter, also referred to as nozzles) for ink of the same color is provided. Inkjet recording devices are known.

In such a recording device provided with a plurality of recording heads or a plurality of nozzle rows, a desired color tone may not be obtained in the recorded image due to the difference in the ejection characteristics of the individual recording heads or the nozzle rows. One of the causes is that there is or occurs a difference in ejection characteristics for each recording head or each nozzle row. This is because the density value of the recorded image changes due to the difference in ejection characteristics.

Factors that cause the ejection characteristics to differ for each recording head or nozzle row include variations in the amount of heat generated by the heating heater that ejects ink (or the thickness of the heating heater) and variations in the diameter of the nozzle that ejects ink. Be done. Fluctuations in the amount of heat generated by the heating heater due to aging and fluctuations in the viscosity of the ink due to differences in the usage environment may also cause differences in the amount of ink ejected, resulting in changes in the recording characteristics formed on the recording medium.

Color shift correction processing is known as a technique for dealing with the difference in color tone caused by the difference in ejection characteristics for each nozzle row or each recording head as described above.

The color shift correction processing is performed, for example, by changing the γ table used in the γ correction processing performed as a part of the image processing in order to correct the ejection characteristics of the recording head. Specifically, a pattern is recorded on a recording medium using a plurality of recording heads or nozzle rows, and the table used in the gamma correction process is reset to an appropriate one based on the recording result of the pattern.

Then, as a method of detecting color shift in the recorded pattern, there is a method of detecting the recorded pattern using an input device such as a scanner. Patterns are recorded for each of the C, M, Y, and K color materials, and each pattern is read by a scanner, colorimeter, densitometer, etc. mounted on the recording device, and the deviation between the read value and the expected value of the pattern is detected. However, there is known a method of correcting a tint, which includes changing a value such as a γ value based on the deviation (see, for example, Patent Document 1).

Further, if the reading cannot be obtained correctly for some reason, an erroneous correction is performed. Therefore, a method for preventing inappropriate density correction based on an abnormal reading is known (for example, Patent Documents). 2).

Japanese Unexamined Patent Publication No. 2004-167947 Japanese Unexamined Patent Publication No. 2008-091966

However, in Patent Document 2, it is determined whether or not the reading value is normally read based on whether or not the reading value is within a predetermined range. Not always possible.

For example, if paper floating occurs during reading, the rise of the density value, which is the reading value of the low gradation portion, may be low, but if it is within a predetermined range, erroneous measurement cannot be detected.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a method for preventing color shift that occurs when an abnormal reading value cannot be corrected normally. More specifically, it is an object of the present invention to provide a method of notifying the user when it is determined that a color shift has occurred and prompting the user to adjust the color shift again.

In order to solve the above problems, the present invention has the configuration described in any of the following.

1: An inkjet recording apparatus having a color shift correction function, which is an adjustment pattern recording means for forming two or more color shift correction adjustment patterns having different densities on a print medium, and two or more adjustment pattern recording means on the print medium. A measurement value acquisition means for acquiring measurement values of adjustment patterns having different densities, a reference table holding means for holding a predetermined color reference value corresponding to two or more adjustment patterns having different densities, and the above two. An output correction value generating means that generates an output correction value for color shift correction based on the above measured values and the reference table, and a threshold value holding that holds a threshold value for determining the success or failure of the predetermined output correction value. The means, the output correction value success / failure determination means for comparing the output correction value with the threshold value and determining the success / failure of the color shift correction, the output correction value success / failure result storage means for storing the success / failure determination result of the output correction value, and the means. After the output correction value is generated, the output correction value success / failure determination means calculates the difference of the output correction value in each gradation value corresponding to the adjustment patterns having two different densities, and the difference of the output correction value is If it is smaller than the threshold value, it is determined that the output correction value is normal, and if it is larger than the threshold value, it is determined that the output correction value is abnormal. It is characterized in that it is applied to and outputs image data.

2: It further has an output correction value success / failure notification means for notifying the result stored in the correction result storage means, and does not notify when the correction value is determined to be normal, and the correction value is determined to be abnormal. The inkjet recording apparatus according to 1 above, wherein the user is notified in the case of such a case.

3: The inkjet recording apparatus according to claim 1, wherein when the output correction value is determined to be abnormal, the output of image data is temporarily stopped.

4: The inkjet recording apparatus according to 1 above, wherein the threshold value for determining the success or failure of the output correction value determined in advance differs for each ink color.

5: The threshold value for determining the success or failure of the output correction value determined in advance differs depending on the recording method of the adjustment pattern recording means, and the threshold value of the recording method having a large number of recording passes per unit area is The inkjet recording apparatus according to 1 above, wherein the number of recording passes per unit area is smaller than that of a recording method.

According to the above configuration, it is possible to notify the user of the color shift that occurs due to an abnormal reading value that cannot be corrected normally, and prompt the user to readjust.

It is a block diagram which shows the structure of a recording apparatus and a recording system. It is a perspective view of a recording device. It is a front view which looked at the recording head from the discharge port surface. It is a block diagram which shows the control composition of a recording apparatus. It is a schematic diagram which showed the structure of a multipurpose sensor. It is explanatory drawing of the control circuit which processes the input / output signal of a sensor. It is explanatory drawing for demonstrating the flow of processing of image data. It is a flowchart which showed the process of acquiring the density characteristic of the recorded matter of a printer. It is the schematic which shows the position which reads the patch pattern and the recording medium which does not record. It is explanatory drawing which generates 1-dimensional LUT for color shift correction. It is a flowchart explaining the flow of image output. It is a flowchart which showed the flow of the 1-dimensional LUT abnormality determination processing for color shift correction. It is a graph which showed the target table and the patch read density table in the example of normal LUT generation. It is a graph which showed the one-dimensional LUT in the example of normal LUT generation. It is a graph which showed the change amount of one-dimensional LUT in the example of normal LUT generation. It is a graph which showed the target table and the patch read density table in the example of an abnormal LUT generation. It is a graph which showed the one-dimensional LUT in the example of an abnormal LUT generation. It is a graph which showed the change amount of one-dimensional LUT in the example of abnormal LUT generation. It is a flowchart explaining the flow of the image output in Example 2. It is a graph which showed the threshold value used for the one-dimensional LUT abnormality determination processing for color shift correction in Example 3. FIG.

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

FIG. 1 is a block diagram showing a configuration of a recording system according to a first embodiment of the present invention. The host device 100 is an information processing device connected to the recording device 200, such as a personal computer or a digital camera. The host device 100 includes a CPU 10, a memory 11, a storage unit 13, an input unit 12 such as a keyboard and a mouse, and an interface 14 for communication between the recording device 200. The CPU 10 executes various processes according to the program stored in the memory 11. These programs are supplied from an external device such as a CD-ROM for storage by the storage unit 13, or are stored in the storage unit 13 in advance.

The host device 100 is connected to the recording device 200 via the interface 14, and transmits the recording data represented by R, G, and B in the image processing step described later and the table for subsequent image processing to the recording device 200. do. Based on the transmitted image processing information, the recording device 200 executes image processing such as color processing and binarization processing, which will be described later, and correction processing of recording characteristics according to the present embodiment. In addition, it is possible to record the recorded data that has undergone image processing.

FIG. 2 is a schematic perspective view showing the mechanical configuration of the recording device 200. A plurality of recording media 1 such as recording paper and a plastic sheet are laminated on a cassette (not shown), and are separated and supplied one by one by a paper feed roller (not shown) at the time of recording. The paper-fed recording medium is arranged in the arrow A direction (hereinafter, transport direction, sub-scanning direction) at a timing corresponding to the scanning of the recording head by the first transport roller 3 and the second transport roller 4 arranged at regular intervals. Also referred to as), a predetermined amount is conveyed. The first transfer roller 3 includes a pair of rollers, a drive roller driven by a stepping motor (not shown) and a driven roller that rotates with the rotation of the drive roller. Similarly, the second transfer roller also consists of a pair of rollers. The recording device 200 can also record on a roll-shaped recording medium in addition to the recording medium stacked on the cassette and cut to a predetermined size.

The recording head 5 mounted on the carriage 6 is an inkjet recording head that ejects inks of each color of CMYK for recording. In the recording head 5 of this embodiment, nozzle rows for ejecting ink are arranged in parallel in the scanning direction. Ink is supplied to the recording head 5 from an ink cartridge (not shown). Then, the recording head 5 ejects ink of each color from each nozzle (ejection port) forming a nozzle row by being driven in response to the ejection signal. That is, an electric heat conversion element (heater) is provided in each nozzle for ejecting ink, and bubbles are generated in the ink by utilizing the thermal energy generated by driving the electric heat conversion element in response to the ejection signal. It is generated and ink is ejected by the pressure of the bubbles.

The driving force of the carriage motor 2 is transmitted to the carriage 6 via the belt 7 and the pulleys 8a and 8b. As a result, the carriage 6 reciprocates along the guide shaft 9 in the direction of arrow B (hereinafter, also referred to as the main scanning direction), whereby the recording head 5 can be scanned. Further, a multipurpose sensor described later is mounted on the side surface of the carriage 6. The multipurpose sensor is used for detecting the density of ink ejected to a recording medium, detecting the width of the recording medium, detecting the distance from the recording head to the recording medium, and the like.

In the above configuration, the recording head 5 ejects ink from the recording head in response to an ejection signal while reciprocating scanning in the main scanning direction to form ink dots on the recording medium 1 for recording (hereinafter,). , Also referred to as recording scanning.) The recording head 5 moves to the home position as necessary, and recovers from a discharge failure state due to clogging of the discharge port or the like by performing a recovery operation by the discharge recovery device provided at the home position position. After the recording scan by the recording head 5, the transport rollers pairs 3 and 4 are driven to transport the recording medium 1 in a predetermined amount in the direction of arrow A. By alternately repeating the recording scan of the recording head 5 and the transport operation of the recording medium, it is possible to record an image or the like on the recording medium 1.

FIG. 3 is a front view of the recording head 5 of this embodiment as viewed from a surface in which an ink ejection port (nozzle) is arranged. It has a recording head having a plurality of nozzle rows for ejecting ink of one color. In FIG. 3, the recording head 5 is provided with five nozzle rows 5a to 5d along the scanning direction. Each nozzle row is formed of 10 nozzles, and the nozzle row 5a contains cyan (C) ink, 5b contains magenta (M) ink, 5c contains yellow (Y) ink, and 5d contains black (K) ink. Be supplied.

The number of nozzles and the number of nozzle rows are not limited to these numbers.

Further, the types of ink colors are not limited to these types.

FIG. 4 is a block diagram showing a control configuration of the recording device 200. The control unit 20 includes a CPU 20a, a ROM 20c, a RAM 20b, and the like such as a microprocessor as memories. The ROM 20c stores various data such as a control program of the CPU 20a and parameters required for recording operation. The RAM 20b is used as a work area of the CPU 20a, and temporarily stores various data such as image data received from the host device 100 and generated recorded data. Further, the ROM 20c stores a LUT (look-up table) as a table to be described later with reference to FIG. 7, and the RAM 20b stores patch pattern data for recording a patch pattern. The LUT may be stored in the RAM 20b, and the patch pattern data may be stored in the ROM 20c.

The control unit 20 inputs and outputs data and parameters used for recording image data and the like to and from the host device 100 via the interface 21, and various information (for example, character pitch, character type, etc.) is input from the operation panel 22. Performs input processing. Further, the control unit 20 outputs ON / OFF signals for driving the motors 23 to 26 via the interface 21. Further, a discharge signal or the like is output to the driver 28 to control the drive for ink discharge in the recording head.

The control system also includes an interface 21, an operation panel 22, a multipurpose sensor 29, and drivers 27 and 28. The driver 27 drives the carriage driving motor 23, the paper feed roller driving motor 24, the first transport roller pair driving motor 25, and the second transport roller pair driving motor 26 according to the instructions from the CPU 20a. The driver 28 drives each of the recording heads 5.

5 (a) and 5 (b) are block diagrams showing the multipurpose sensor 29. FIG. 5A shows a plan view of the multipurpose sensor 29, and FIG. 5B shows a cross-sectional view.

The measurement area of the multipurpose sensor 29 is located downstream of the recording surface of the recording head 5, and the lower surface of the multipurpose sensor 29 is arranged so as to be at the same position as or higher than the lower surface of the recording head 5. There is. The multipurpose sensor 29 includes two phototransistors 203 and 204, three visible LEDs 205, 206 and 207, and one infrared LED 201 as optical elements, and each element is driven by an external circuit (not shown). Will be done. All of these elements are bullet-type elements (general mass-produced type with a size of φ3.0 to 3.1 mm) having a maximum diameter of about 4 mm.

In this embodiment, the straight line connecting the center point of the irradiation range of the irradiation light emitted from the light emitting element to the measurement surface and the center of the light emitting element is referred to as an optical axis of the light emitting element or an irradiation axis. This irradiation axis is also the center of the luminous flux of the irradiation light.

The infrared LED 201 has an irradiation angle of 45 degrees with respect to the surface (measurement surface) of the recording medium parallel to the XY plane. The irradiation axis, which is the center of the irradiation light, is arranged so as to intersect the sensor center axis 202 parallel to the normal line (Z axis) of the measurement surface at a predetermined position. The position of this intersecting position (intersection) on the Z axis is defined as the reference position, and the distance from the sensor to the reference position is defined as the reference distance. The width of the irradiation light of the infrared LED 201 is adjusted by the opening, and it is optimized to form an irradiation surface (irradiation region) having a diameter of about 4 to 5 mm on the measurement surface at the reference position.

The two phototransistors 203 and 204 are sensitive to light of wavelengths from visible to infrared. When the measurement surface is in the reference position, the phototransistors 203 and 204 are installed so that their light receiving axes are parallel to the reflection axis of the infrared LED 201. That is, the light receiving shaft of the phototransistor 203 is arranged so as to be moved by +2 mm in the X direction and +2 mm in the Z direction with respect to the reflection shaft. Further, the light receiving shaft of the phototransistor 204 is arranged so as to be moved by -2 mm in the X direction and -2 mm in the Z direction.

When the fixed surface is in the reference position, the intersection of the measurement surface and the irradiation axis of the infrared LED 201 and the visible LED 205 coincides, and the light receiving regions of the two phototransistors 203 and 204 at this position are formed so as to sandwich the intersection. Will be done. A spacer with a thickness of about 1 mm is sandwiched between the two elements so that the light received from each other does not wrap around. An opening is also provided on the phototransistor side to limit the incoming light range, and its size is optimized so that only reflected light with a diameter of 3 to 4 mm on the measurement surface at the reference position can be received. Be transformed. In this embodiment, on the measurement surface (measurement target surface), the line connecting the center point of the region (range) in which the light receiving element can receive light and the center of the light receiving element is defined as the optical axis of the light receiving element or light receiving. Called the axis. This light receiving shaft is also the center of the light flux of the reflected light reflected by the measuring surface and received by the light receiving element.

In FIGS. 5 (a) and 5 (b), the LED 205 is a monochromatic visible LED having a green emission wavelength (about 510 to 530 nm) and is installed so as to coincide with the sensor central axis 202. Further, the LED 206 is a monochromatic visible LED having a blue emission wavelength (about 460 to 480 nm), and as shown in FIG. 5 (a), the LED 206 is moved to a position moved by +2 mm in the X direction and -2 mm in the Y direction with respect to the visible LED 205. Have been placed.

Then, when the measurement surface is in the reference position, it is arranged so as to intersect the light receiving axis of the phototransistor 203 at the intersection position between the irradiation axis of the visible LED 206 and the measurement surface. Further, the LED 207 is a monochromatic visible LED having a red emission wavelength (about 620 to 640 nm), and is located at a position separated from the visible LED 205 by -2 mm in the X direction and +2 mm in the Y direction as shown in FIG. 5 (a). It is in. Then, when the measurement surface is in the reference position, it is arranged so as to intersect the light receiving axis of the phototransistor 204 at the intersection position between the irradiation axis of the visible LED 207 and the measurement surface.

FIG. 6 shows a schematic diagram of a control circuit that processes input / output signals of each sensor of the multipurpose sensor 29 according to this embodiment. The CPU 301 outputs an on / off control signal of the infrared LED 201 and the visible LEDs 205 to 207, calculates an output signal obtained according to the amount of light received by the phototransistors 203 and 204, and the like. The drive circuit 302 receives an ON signal sent from the CPU 301 and supplies a constant current to each light emitting element to emit light, or adjusts the amount of light emitted by each light emitting element so that the amount of light received by the light receiving element becomes a predetermined amount. Or something. The I / V conversion circuit 303 converts the output signal sent as a current value from the phototransistors 203 and 204 into a voltage value. The amplifier circuit 304 functions to amplify the output signal after conversion to a voltage value, which is a minute signal, to an optimum level in A / D conversion. The A / D conversion circuit 305 converts the output signal amplified by the amplifier circuit 304 into a 10-bit digital value and inputs it to the CPU 301. The memory (non-volatile memory, etc.) 306 is used for recording a reference table for deriving a desired measured value from the calculation result of the CPU 301 and for temporarily storing an output value. As the CPU 301 and the memory 306, the CPU 20a and the RAM 20b of the recording device may be used.

Next, an image processing method for generating the recorded data used in the recording device 200 by the host device 100 and the recording device 200 will be described.

FIG. 7 is a block diagram showing a configuration of image processing of this embodiment. In the image processing of this embodiment, image data (luminance data) of 8 bits (256 gradations each) for each color of red (R), green (G), and blue (B) is input. Finally, each nozzle recorded by the nozzle trains 5a to 5e is processed to be output as 1-bit bit image data (recorded data). The type of color and the gradation of color are not limited to this value.

First, image data represented by R, G, and B multi-valued luminance signals is transmitted from the host device 100 to the recording device 200.

Subsequently, the image data represented by the R, G, and B multi-valued luminance signals is converted into the R, G, and B multi-valued data using the multidimensional LUT 401. This color space conversion pre-processing (hereinafter, also referred to as pre-stage color processing) is between the color space of the input image represented by the image data of R, G, and B in the recording target and the color space reproducible by the recording device 200. It is done to correct the difference between.

The data of each color of R, G, B subjected to the pre-stage color processing is received from the host device using the multidimensional LUT402, and the data of each color of R, G, B subjected to the pre-stage color processing is the ink color C, Convert to multi-valued data of M, Y, K. This color conversion process (hereinafter, also referred to as post-stage processing) is a process of converting the RGB image data of the input system represented by the brightness signal into the CMYK image data of the output system for expressing the density signal. be.

Next, the output γ correction of the multi-valued data of C, M, Y, and K subjected to the subsequent color processing is performed by the one-dimensional LUT403 of each color. Normally, the number of dots recorded per unit area of a recording medium and the recording characteristics such as the reflection density obtained by measuring the recorded image do not have a linear relationship. Therefore, the input gradation levels of C, M, Y, and K are multi-valued so that the input gradation level of 10 bits each of C, M, Y, and K and the density level of the image recorded by the input gradation level have a linear relationship. The output γ correction process for correcting the above is performed.

As described above, as the output gamma correction table (one-dimensional LUT403), one created for a recording head showing standard recording characteristics is often used. However, as described above, there are individual differences in the ejection characteristics of the recording head or nozzle. Therefore, it is not possible to perform appropriate density correction for all recording heads or nozzles only with an output gamma correction table that corrects the recording characteristics of a recording head or nozzle showing standard discharge characteristics.

Therefore, in this embodiment, the colors created based on the density characteristics or glossiness information acquired in the color shift correction processing step described later for the multi-valued data of C, M, Y, and K to which the output gamma correction has been performed. Color deviation correction processing is performed using the deviation correction table (one-dimensional LUT404).

After that, the quantization process 405 is performed by halftone processing using error diffusion, dither pattern, etc. and Index expansion, and is output as data recorded by the recording head.
Subsequently, the one-dimensional LUT404 for color shift correction will be described. The one-dimensional LUT for color shift correction is set based on the density value information or glossiness information for each nozzle row acquired in the color shift correction processing step.

FIG. 8 is a flowchart showing the operation flow of the recording device 200 for the process of acquiring the density characteristic of the recorded matter of the printer in the color shift correction processing step. A color shift correction processing start command for recording a patch pattern and measuring the density is input from the input unit 12 of the host device 100, the CPU 10, the operation panel 22 of the recording device 200, or the like (S801). When the instruction to execute the color shift correction process is input, the CPU 20a of the recording device 200 drives the paper feed motor 24 to start supplying the recording medium from the paper feed tray (S802). When the recording medium is conveyed to an area where recording by the recording head is possible, the operation of conveying the recording medium in the sub-scanning direction and the recording scanning in the main scanning direction of the carriage 6 that drives the carriage motor 23 are alternately performed. Then, the recording head 5 as the patch pattern recording means records the patch pattern for acquiring the characteristics of each nozzle on the recording medium (S803).

Next, in order to dry the recorded patch pattern, a timer counter for waiting for a predetermined time is started (S804).

Subsequently, the reflection intensity measurement of the white level (ground color of the recording medium) in which the patch pattern is not recorded is started using the green LED 205, the blue LED 206, and the red LED 207 of the multipurpose sensor 102 (S805). The white level measurement result is used as a reference white when calculating the density value of the patch pattern to be recorded later. Therefore, the white level value is held for each LED. Here, the density of the blank portion of the recording medium on which the patch pattern is not recorded is measured by measuring the background color of the recording medium, and if the recording medium is white, the background color is white. In this embodiment, an example using a recording medium having a white background will be described.

After it is confirmed that the counter of the drying timer has elapsed for a predetermined time (S806), the reflection intensity measurement of the patch pattern is started (S807). In the reflection intensity measurement, among the LEDs 205 to 207 mounted on the multipurpose sensor 102, the LED suitable for the ink color to be measured for density is turned on, and the light is reflected by the phototransistors 203 and 204 as measuring means for measuring the density of the patch pattern. This is done by reading the light. The green LED 205 lights up when measuring, for example, a patch pattern recorded by M ink and a blank portion (ground color of the recording medium) on which the patch pattern is not recorded. Further, the blue LED 206 lights up when measuring, for example, a patch pattern recorded with Y ink and K ink, and a blank portion (ground color of the recording medium) on which the patch pattern is not recorded. Further, the red LED 207 lights up when measuring, for example, a patch pattern recorded by C and a blank portion (ground color of the recording medium) on which the patch pattern is not recorded.

When the reading of the patch pattern is completed, the density value of the patch pattern is calculated for each corresponding nozzle based on the output values from both the patch pattern and the white level (ground color of the recording medium) (S808). The ink color using the green LED 205 at the time of patch reading uses the white level output value read by the green LED 205. The ink color using the blue LED 206 at the time of patch reading uses the white level output value read by the blue LED 206. The ink color using the red LED 207 at the time of patch reading uses the white level output value read by the red LED 207.

The density value can be calculated by multiplying the reflection intensity of the patch when the reflection intensity of the white paper is 100% by a logarithm. Specifically, for example, the density of a patch recorded with M ink can be calculated by the following formula.

When the white level = Gw and the patch reading value = Gm read by the green LED 205, the density value ODm = -log (Gm / Gw).

Subsequently, each concentration value is stored in the memory 306 or RAM 20b in the recording device main body (S809), the recording medium is discharged (S810), and the processing is completed.

FIG. 9 is a schematic view showing a patch pattern recorded by the recording device 200 and read by the multipurpose sensor 102 and a position where the recording medium not recorded is read by the multipurpose sensor 102.
FIG. 9 (1) is a diagram showing the relationship between patch patterns in which the letters Pa to Pd are recorded by the ink ejected from the nozzle rows 5a to 5d, respectively.

The numbers 1 to 5 rank the density gradations of the patches to be recorded.
Specifically, for example, Pa1 is a patch for recording an image having a gradation value of 1 rank using a 5a nozzle. The gradation value is not limited to five values. Also, the size of the numbers and the height of the gradation are not always related.

FIG. 9 (2) is a diagram showing the relationship between the recorded patch pattern and the LEDs 205 to 207 that read the white level. W1 to W5 indicate positions for reading the white level, and are not recorded.

The one-dimensional LUT 404 for color shift correction has a white level in the color shift correction processing step of FIG. 8, a density value of each patch pattern shown in FIG. 9 obtained by patch reading, and a predetermined predetermined value called a target value. Generated by comparing with the target concentration. The correction value is calibrated so that the density recorded in each nozzle row on the recording medium approaches the target value.

As the target value, a density value or glossiness obtained by reading a patch pattern recorded in advance using an inkjet recording device and a recording head having good accuracy can be adopted. In this way, the target value is a value extremely close to the ideal value.

FIG. 10 shows an example of generating a one-dimensional LUT404 for color shift correction.

B101 of FIG. 10 shows a Pa patch pattern consisting of patches Pa1 to Pa5 recorded by a 5a nozzle using LED 207, and a density value and a target value obtained by reading the white level of W1 to W5.

As the white level when determining the density value of Pa1, the value of W1 may be used, or the value obtained by averaging the values of W1 to W5 may be used.

T101 shows a one-dimensional LUT for color shift correction for a 5a nozzle generated based on B101.

Here, since the read density value is higher than the target value, a one-dimensional LUT table 404 is created and set so that the output value is lower than the input value for the image data of the 5a nozzle. do.

Similarly, a one-dimensional LUT for color shift correction for the 5b nozzle is generated from the density value and the target value of the Pb patch pattern, and a one-dimensional LUT for color shift correction for the 5c nozzle is generated from the density value and the target value of the Pc patch pattern. A one-dimensional LUT for color shift correction for a 5d nozzle is generated from the density value and the target value of the Pd patch pattern.

A separate one-dimensional LUT for color shift correction may be created for each recording medium, print resolution, and usage environment.

Further, the color shift correction processing step of FIG. 8 and the printing of the patch pattern of FIG. 9 (1) do not have to be completed in each processing, and may be continuously performed in one feeding / discharging.

FIG. 11 is a flowchart illustrating a flow of image output by the host 100 and the recording device 200. First, the recording device 200 converts the image data represented by the R, G, and B multi-valued luminance signals received from the host device 100 into R, G, and B multi-valued data using the multidimensional LUT 401. (S1101). Next, the data of each color of R, G, and B subjected to the pre-stage processing using the multidimensional LUT 402 is converted into the data of C, M, Y, and K multi-values which are ink colors (S1102). Then, the output γ correction of the C, M, Y, and K multi-valued data subjected to the post-stage processing is performed by the one-dimensional LUT403 of each color (S1103). Next, the C, M, Y, and K multi-valued data are subjected to color shift correction processing by the one-dimensional LUT404 for color shift correction (S1104).

Subsequently, it is determined whether or not the color shift correction process based on the normal reading value, which is the point of this embodiment, is performed based on the shape of the color shift correction one-dimensional LUT404 (S1105). The determination process of S1105 is a point of this embodiment, and will be described in detail later.

When it is determined that the shape of the one-dimensional LUT 404 for color shift correction is abnormal, the determination result is stored in the main body memory, and the fact is displayed on the main body panel to notify the user (S1106). The method of notifying the user is not limited to the display on the main body panel, and any method can be used as long as it can be transmitted to the user, for example, displaying on the PC screen for transmitting image data or blinking the display LED. It doesn't matter. In this embodiment, the image output is not stopped due to the notification, the print (S1108) is continued after the quantization process (S1107), and the output result is confirmed by the user after the paper ejection (S1109). It is possible to prompt the user to decide whether to perform the color shift correction process again after the output is completed.

When the judgment result is judged to be normal, the judgment result is stored in the main body memory, and the calculated multi-valued data for each of C, M, Y, and K is processed for halftone using error diffusion and dither pattern, and index expansion. Quantization processing is performed by (S1109).

Next, with reference to FIGS. 12 to 18, a one-dimensional LUT abnormality determination process for color shift correction, which determines whether or not the shape of the one-dimensional LUT 404 for color shift correction shown in S1105, which is the point of this embodiment, is abnormal will be described. ..

FIG. 12 is a flowchart showing the flow of the one-dimensional LUT abnormality determination process for color shift correction.

In S1201, the one-dimensional LUT 404 for color shift correction created by the method shown in the example of FIG. 11 is read out.

For the sake of explanation, first, a case where a normal one-dimensional LUT for color shift correction is generated will be described.

Tt in FIG. 13 (1) is a target table for each gradation of C ink. Ta is a patch reading density table in which the density values obtained by reading patches Pa1 to Pa5 are plotted in the order of gradations 1 to 5.

Using two density tables, the input value for realizing the same value as the density of the target table in each gradation value with Ta is obtained. Hereinafter, a detailed description will be given using tone 1. The density of the target table Tt at the input value X1 of the tone 1 is Y1. The input value of the patch reading density table Ta equal to Y1 is Z1. Similarly, for gradations 2 to 5, the input value Z2 corresponding to the input value X2, the input value Z3 corresponding to the input value X3, the input value Z4 corresponding to the input value X4, and the input value Z5 corresponding to the input value X5 are calculated. ..

FIG. 14 is a graph in which the above-mentioned input value X is on the horizontal axis and the input value Z is on the vertical axis, and is an input value conversion table for outputting the density value of the target table Tt in the patch reading density table Ta. It becomes a one-dimensional LUT404. Here, for convenience of explanation, it is expressed as one-dimensional LUTTa.

Th of FIG. 13 (2) is a patch reading density table in which the density values obtained by reading patches Pa1 to Pa5 using the ejection amount upper limit head at each gradation of C ink are plotted in the order of gradations 1 to 5.

Similarly, Tl in FIG. 13 (3) is a patch reading density table in which the density values obtained by reading patches Pa1 to Pa5 using the ejection amount lower limit head at each gradation of C ink are plotted in the order of gradations 1 to 5.

The discharge amount upper limit (lower limit) head takes into consideration variations in head manufacturing. Since there is a variation in the discharge amount as the main cause of the color shift generated in the inkjet recording device, in this embodiment, whether or not to deviate from the correction LUT created from the maximum value (minimum value) of the head manufacturing tolerance is determined. It is used as a guideline for determining the abnormality of the correction LUTTa of interest.

LUTTh in FIG. 14 is a one-dimensional LUT calculated from the concentration table Th in the discharge amount upper limit head, and LUTTl is a one-dimensional LUT calculated from the concentration table Tl in the discharge amount lower limit head.

In S1202, the amount of change between adjacent gradations in each LUT shown in FIG. 14 is calculated.

FIG. 15 is a graph showing the amount of change. The horizontal axis indicates the gradation of the patch. For example, the gradation 2-1 indicates that the patch Pa1 and the patch Pa2 are focused on. The vertical axis shows the difference in the input value Z between the patches of interest.

Da indicates the amount of change between adjacent gradations of the one-dimensional LUTTa for color shift correction. Similarly, Dh indicates the amount of change in LUTTh in the head with a large discharge amount, and Dl indicates the amount of change in LUTTl in the head with a small discharge amount.

Since the main cause of the color shift is the variation in the discharge amount, the density curve in the discharge amount head within the manufacturing tolerance falls within the density curve in the head at the upper and lower limits of the manufacturing tolerance. Further, when there are few factors other than the head discharge amount, which is the main cause of the density variation, the inclination of the density curve also falls within the range of the upper and lower limit heads of the manufacturing tolerance. That is, when the one-dimensional LUT is normally generated, the inclination of the LUT also falls within the range of the upper and lower limits of the manufacturing tolerance. Therefore, in this embodiment, the success or failure of the one-dimensional LUT for color shift correction is determined by paying attention to the amount of change between the gradations of each correction LUT.

In S1203, it is determined whether or not the amount of change between the gradations of the one-dimensional LUT to be determined exceeds the threshold value. In this embodiment, the amount of change between the gradations of the one-dimensional LUT in the head at the upper and lower limits of the manufacturing tolerance is used as the threshold value.

The threshold value is not limited to the head with the upper and lower limits of the manufacturing tolerance, and the optimum threshold value in the system can be used. For example, the threshold value on the lower limit side of the tolerance may be widened in anticipation of a decrease in the discharge amount due to wear, or the LUT for color shift correction can be calculated for each recording medium. The range of the judgment threshold value may be narrowed, or the like.

In FIG. 15, since the amount of change Da between the gradations of the determined one-dimensional LUTTa does not exceed the threshold value, the shape of the one-dimensional LUTTa is determined to be normal (S1204), and the shape of the one-dimensional LUT404 for color shift correction of S905 is determined. End the anomaly determination step.

Subsequently, a case where an abnormal one-dimensional LUT404 for color shift correction is generated will be described (hereinafter, for convenience of explanation, it is expressed as one-dimensional LUTtb).

Here, as an example of the case where abnormal color shift correction is generated, a case where paper floating occurs will be described.

First, in S1201, the one-dimensional LUTTb described later is read out.

Tt in FIG. 16 is a target table for each gradation of C ink. Tb is a patch reading density table in which the density values when paper floating occurs when the patches Pa1 to Pa5 are read are plotted in the order of gradations 1 to 5.

FIG. 17 is a one-dimensional LUTTb created from the concentration table Tb. Further, LUTTh is a one-dimensional LUT calculated from the concentration table Th in the discharge amount upper limit head, and LUTTl is a one-dimensional LUT calculated from the concentration table Tl in the discharge amount lower limit head, which are the same as those shown in FIG.

In S1202, the amount of change between adjacent gradations in each LUT shown in FIG. 17 is calculated.

FIG. 18 is a graph showing the amount of change. The horizontal axis and the vertical axis are the same as those in FIG. Db indicates the amount of change between adjacent gradations of the one-dimensional LUTTb for color shift correction. Dh indicates the amount of change in LUTTh in the head with a large discharge amount, and Dl indicates the amount of change in LUTTl in the head with a small discharge amount.

In FIG. 18, since the amount of change Db between the gradations of the determined one-dimensional LUTTb exceeds the threshold value, the shape of the one-dimensional LUTTb is determined to be abnormal (S1205), and the shape of the one-dimensional LUT404 for color shift correction of S1105 is determined. End the anomaly determination step.

According to the above configuration, the user is notified of color shifts that occur due to abnormal readings that cannot be corrected normally, prompting the user to check the output, and readjusting if the image quality of the output is unsatisfactory. Can be encouraged.

In the second embodiment, as compared with the first embodiment, when the shape of the one-dimensional LUT 404 for color shift correction is determined to be abnormal, a configuration is added that prompts a determination as to whether or not to continue the output.

FIG. 19 is a flowchart illustrating a flow of image output by the host 100 and the recording device 200. Since S1901 to S1906 are the same operations as S1101 to S1106 in FIG. 11, the description thereof will be omitted.

When it is determined in S1905 that the shape of the one-dimensional LUT404 for color shift correction is abnormal, the user is notified in S1906 and the print is put into a standby state in S1907.

If the user decides to continue printing after prompting the user for confirmation in the standby state, the printing is continued by operating the main body or the PC (S1909). After that, when the output is completed, the paper is ejected (S1911).

On the other hand, when the user wants to cancel the printing, the printing is stopped by operating the main body or the PC (S1910).

In this way, when the shape of the one-dimensional LUT404 for color shift correction is determined to be abnormal, it is possible to prevent unnecessary consumption of recording media for users who are particular about image quality by prompting confirmation before starting output. ..

In the third embodiment, as compared with the first embodiment, the threshold value for determining the shape of the one-dimensional LUT 404 for color shift correction is changed according to the density patch recording method in the color shift correction processing step. I'm adding.

FIG. 20 is a graph showing the relationship between the density patch recording method and the threshold value in the color shift correction processing step.

When the density patch recording method is 8 passes, the Dh and Dl thresholds shown in FIG. 15 are applied. On the other hand, when the number of recording passes is 2, Dl2 in which the threshold value on the upper limit side is larger than Dl and Dh2 in which the threshold value on the lower limit side is smaller than Dh are applied.

Further, when the number of recording passes is 16, Dl16 in which the threshold value on the upper limit side is smaller than Dl and Dh16 in which the threshold value on the lower limit side is larger than Dh are applied.

When the number of recording passes is 2, the ink landing position is deteriorated compared to 8 passes, the number of ink dots ejected at the same time increases, and the ink dots move adjacently and minutely on the recording medium. Due to a phenomenon such as ink loss, the variation in recording density becomes large. Therefore, in addition to the head discharge amount tolerance, which is the main cause of the density variation in the first embodiment, there are more factors that cause the density variation. As a result, if the threshold value is the same as that of 8 passes, the number of cases where the shape of the one-dimensional LUT 404 for color shift correction is determined to be abnormal increases.

Therefore, in the third embodiment, the shape determination accuracy of the one-dimensional LUT for color shift correction can be improved by widening the threshold range in two passes.

Similarly, in 16-pass recording, the variation in the recording density is small, so that the determination can be made only for the head discharge amount tolerance, which is the main cause of the density variation. That is, by narrowing the threshold range in 16 passes, the shape determination accuracy of the one-dimensional LUT for color shift correction can be improved.

The present invention is applicable to all devices that use recording media such as paper, cloth, leather, non-woven fabric, OHP paper, and metal. Specific applicable equipment includes office equipment such as printers, copiers and facsimiles, and industrial production equipment.

10 CPU
11 Memory 12 Input unit 13 Storage unit 14 Interface 100 Host device 200 Recording device

Claims (5)

An inkjet recording device with a color shift correction function.
An adjustment pattern recording means for forming two or more color shift correction adjustment patterns having different densities on a print medium,
A measurement value acquisition means for acquiring measurement values of two or more adjustment patterns having different densities on the print medium, and
A reference table holding means for holding a predetermined color reference value corresponding to two or more adjustment patterns having different densities, and a reference table holding means.
An output correction value generating means that generates an output correction value for color shift correction based on the two or more measured values and the reference table.
A threshold holding means for holding a threshold for determining the success or failure of the output correction value determined in advance, and
An output correction value success / failure determination means for comparing the output correction value with the threshold value and determining the success / failure of the color shift correction,
An output correction value success / failure result storage means for storing the success / failure judgment result of the output correction value, and
Have,
After the output correction value is generated, the output correction value success / failure determination means
The difference of the output correction value in each gradation value corresponding to the two adjustment patterns with different densities is calculated, and if the difference of the output correction value is smaller than the threshold value, the output correction value is judged to be normal, and if it is larger than the threshold value. Is an inkjet recording apparatus characterized in that an output correction value is determined to be abnormal, the determination result is stored in the correction result storage means, and the output correction value is applied to an input image to output image data. It also has an output correction value success / failure notification means for notifying the user of the result stored in the correction result storage means.
The inkjet recording apparatus according to claim 1, wherein no notification is given when the output correction value is determined to be normal, and notification is given when the output correction value is determined to be abnormal. The inkjet recording apparatus according to claim 1, wherein when the output correction value is determined to be abnormal, the output of image data is temporarily stopped. The inkjet recording apparatus according to claim 1, wherein the threshold value for determining the success or failure of the output correction value determined in advance is different for each ink color. The threshold value for determining the success or failure of the output correction value determined in advance differs depending on the recording method of the adjustment pattern recording means.
The inkjet recording apparatus according to claim 1, wherein the threshold value of the recording method having a large number of recording passes per unit area is smaller than that of the recording method having a small number of recording passes per unit area.

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