JP2014157026A - Image forming apparatus, colorimetry method, and colorimetry program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly perform colorimetry even when a defective image is included in a part of a colorimetry object.SOLUTION: In an image forming apparatus 1, a plurality of nozzles of a recording head 20 discharge ink drops to form a multi-color image on a recording medium, and a nozzle state detection unit detects a missing state of the image formed by the recording head 20. When a colorimetry subject formed on the recording medium by the recording head 20 is imaged by an imaging unit 30 in a predetermined imaging range for colorimetry, the image forming apparatus 1 performs colorimetry on the basis of an imaging result of the imaging unit 30 in an effective imaging range which is obtained by excluding a detected missing range from the imaging range of the imaging unit 30.

Description

  The present invention relates to an image forming apparatus, a color measurement method, and a color measurement program. Concerning color programs.

  Image forming apparatuses such as color ink jet type image forming apparatuses and color electrophotographic image forming apparatuses are offset by advertising media and pamphlets that require a high image but a relatively small number of copies as the image quality improves. It is also used for printing.

  In offset printing that requires high image quality, the color of the printed matter requested by the customer may differ from the color of the print output result that is actually printed out by the image forming apparatus.

  Usually, the customer confirms the color of the printed matter on the display and places an order for printing. However, each image forming apparatus has a color reproduction characteristic specific to each model, which is different from the color confirmed on the display. May result in printing.

  Therefore, conventionally, a technique for performing color reproduction using a color space that does not depend on a device such as a display or an image forming apparatus, such as a Lab color space or an xyz color space, has been used.

  The image forming apparatus controls the amount of color material and the like in order to output a specified color. For example, in an ink jet image forming apparatus, the output color is controlled by controlling the amount of ink discharged from the ink head by calculating and controlling the amount of ink discharged and the print pattern. In the image forming apparatus, the output color is controlled by controlling the amount of toner adhering to the photosensitive member, the amount of laser beam, and the like.

  However, the amount of the color material, for example, the ink discharge amount of the ink jet image forming apparatus varies depending on the state of the nozzle of the head, the viscosity of the ink, the variation of the discharge drive elements (piezo elements, etc.), Variation in color reproducibility occurs. Further, the ink ejection amount of the ink jet type image forming apparatus changes with time in one image forming apparatus or varies for each image forming apparatus. In other words, variations in the color reproduction of the image occur.

  Conventionally, a case, a reference pattern used for colorimetry arranged in the case, and a part of the image pickup region are picked up by the reference pattern, and a colorimetric object is picked up in another region. A two-dimensional sensor; an imaging element that is disposed on the optical path of the reference pattern and the colorimetric object and forms an image of the reference pattern on a sensor surface of the two-dimensional sensor; An imaging apparatus comprising: a transmissive member disposed in an optical path between the sensor and the color measurement object and having a refractive index for setting the imaging position of the color measurement object by the imaging element as the two-dimensional sensor surface Has been proposed (see Patent Document 1).

  That is, in this conventional technique, an image is captured so that the reference pattern and the colorimetric object can be compared, and the color actually measured by the image forming apparatus is measured.

  In the prior art described in the above publication, color measurement is performed by taking an image so that the reference pattern and the color measurement target can be compared.

  However, when a color measurement target is recorded, if a fraudulent image is partially generated from the color measurement target due to nozzle clogging, dust adhesion, or the like due to missing dots or incorrect dot formation, accurate color measurement cannot be performed. In order to perform accurate color measurement, even if the cause of the illegal image is due to a temporary cause, after removing the cause of the illegal image, the incorrect image is recorded again. It must be repeated until no longer formed. As a result, if the work of removing the cause of the illegal image is performed every time the color measurement is performed, the usability is lowered. In addition, if nozzle clogging is caused, the nozzle clogging elimination operation not only increases the ink consumption, but also waits for the colorimetric processing operation during that time, increasing the time required for colorimetry. is there.

  Therefore, an object of the present invention is to accurately perform color measurement even when there is an illegal image in a part of the color measurement object.

  To achieve the above object, an image forming apparatus according to claim 1 detects an image forming unit that forms an image of a plurality of colors on a recording medium, and a defect state of an image formed by the image forming unit. Image defect detection means, image pickup means for picking up an object to be colorimetrically formed on the recording medium by the image forming means over a predetermined image pickup range, and image loss detection among the image pickup ranges by the image pickup means And a colorimetric unit that performs colorimetry based on an imaging result of the imaging unit in the effective imaging range, with a range excluding the missing range detected by the unit as an effective imaging range.

  According to the present invention, color measurement can be accurately performed even when there is an illegal image in a part of the color measurement target.

1 is a schematic perspective view of an image forming apparatus to which a first embodiment of the present invention is applied. The top view of a carriage part. FIG. The schematic front view of an imaging part. The figure which shows the positional relationship of an imaging part and a colorimetry adjustment patch. The schematic perspective view of a nozzle state detection part. The schematic front view of a nozzle state detection part. The schematic plan view of a nozzle state detection part. FIG. 3 is a block diagram of a main part of the image forming apparatus. The block block diagram of a camera controller. Explanatory drawing of acquisition of a reference | standard colorimetric value and imaging reference | standard RGB value from a reference | standard sheet | seat, and a 1st linear transformation matrix acquisition process. Explanatory drawing of a color adjustment process. FIG. 13 is a diagram illustrating color adjustment processing continued from FIG. 12. The figure which shows an example of the color measurement adjustment color patch when there is no nozzle defect | deletion. The figure which shows an example of the color measurement adjustment color patch in case there exists a nozzle defect | deletion. FIG. 4 is a diagram illustrating an example of a recording head used for forming a colorimetric adjustment color patch. The figure which shows an example of the colorimetric adjustment color patch recorded with cyan and yellow when there is a nozzle defect. Explanatory drawing of the recording state of the color measurement adjustment color patch by an interlace method when there exists a nozzle defect. Explanatory drawing of the method of supplementing the data reduction by nozzle defect | deletion. The flowchart which shows a nozzle state detection process. The figure which shows an example of the pattern for nozzle defect | deletion detection. Explanatory drawing of a nozzle defect | deletion detection process from a colorimetry adjustment color pattern. The figure which shows an example of the color measurement adjustment color patch with the nozzle defect | deletion containing a nozzle curvature. The top view of the image pick-up part of the 2nd example. AA arrow sectional drawing of the imaging part of FIG. BB arrow sectional drawing of the imaging part of FIG. The top view of a reference | standard chart. FIG. 6 is a block diagram of a main part of an image forming apparatus according to a second embodiment. The block block diagram of an imaging part and a colorimetry control part. The figure which shows an example of the image data which imaged the reference | standard chart and the imaging target simultaneously. The figure which shows an example of an initial reference value. Explanatory drawing of the color adjustment process of 2nd Example. Explanatory drawing of a 3rd linear transformation matrix production | generation process. The figure which shows the relationship between an initial reference | standard RGB value and the reference | standard RGB value at the time of colorimetry. FIG. 3 is a front cross-sectional view of an imaging unit in which optical path length changing members are arranged on both the colorimetric object imaging side and the reference sheet imaging side. AA arrow sectional drawing of FIG. The front sectional view of the image pick-up part which is not provided with the optical path length change member. Explanatory drawing of the range determination excluded from the colorimetry object of the image by the defect | deletion nozzle based on the imaging optical system of an imaging part. FIG. 2 is a block diagram of a main part of an image forming system to which a color measurement system is applied.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The range of this invention is unduly limited by the following description. However, not all the configurations described in the present embodiment are essential constituent elements of the present invention.

  Note that “Lab (Lab value)” described below means, for example, the CIELAB (CIE 1976 L * a * b *) color space. Hereinafter, for convenience of explanation, “L * a * b *” is represented as “Lab”. The present invention is not limited to the L * a * b * color space, and may be an L * u * v * color space or the like.

  1 to 23 are diagrams showing a first embodiment of an image forming apparatus, a colorimetric method and a colorimetric program according to the present invention. FIG. 1 shows an image forming apparatus, a colorimetric method and a colorimetric program according to the present invention. 1 is a schematic perspective view of an image forming apparatus 1 to which the first embodiment is applied.

  In FIG. 1, an image forming apparatus 1 has a main body housing 2 disposed on a main body frame 3, and a main guide rod in the main scanning direction indicated by a double arrow A in FIG. 4 and the auxiliary guide rod 5 are stretched over. The main guide rod 4 movably supports the carriage 6, and the carriage 6 is provided with a connecting piece 6 a that engages with the sub guide rod 5 to stabilize the posture of the carriage 6. In the image forming apparatus 1, an endless belt-like timing belt 7 is disposed along a main guide rod 4, and the timing belt 7 is stretched between a driving pulley 8 and a driven pulley 9. The driving pulley 8 is rotationally driven by the main scanning motor 10, and the driving pulley 8 is disposed in a state where a predetermined tension is applied to the timing belt 7. The driving pulley 8 is rotationally driven by the main scanning motor 10 to rotate and move the timing belt 7 in the main scanning direction according to the rotation direction.

  The carriage 6 is connected to a timing belt 7, and is reciprocated in the main scanning direction along the main guide rod 4 when the timing belt 7 is rotationally moved in the main scanning direction by the drive pulley 8.

  In the image forming apparatus 1, the cartridge unit 11 and the maintenance mechanism unit 12 are accommodated at both end positions in the main scanning direction in the main body housing 2. In the cartridge unit 11, cartridges that respectively store yellow (Y), magenta (M), cyan (C), and black (K) inks are replaceably stored. Each cartridge of the cartridge unit 11 is connected to recording heads 20y, 20m, 20c, and 20k (see FIG. 2) of the corresponding color of the recording head (image forming unit) 20 mounted on the carriage 6 by a pipe (not shown). . The cartridge unit 11 supplies ink to the recording heads 20y, 20m, 20c, and 20k through a pipe. In the following description, the recording heads 20y, 20m, 20c, and 20k are collectively referred to as the recording head 20.

  As will be described later, the image forming apparatus 1 moves on the platen 14 (see FIG. 2) in the sub-scanning direction (arrow B direction in FIG. 1) perpendicular to the main scanning direction while moving the carriage 6 in the main scanning direction. By ejecting ink onto the recording medium P (see FIG. 2) conveyed intermittently, an image is recorded and output on the recording medium P.

  That is, the image forming apparatus 1 according to the present embodiment intermittently conveys the recording medium P in the sub-scanning direction, and performs the main scanning of the carriage 6 while the conveyance of the recording medium P in the sub-scanning direction is stopped. While moving in the direction, ink is ejected from the nozzle row of the recording head 20 mounted on the carriage 6 onto the recording medium P on the platen 14 to form an image on the recording medium P.

  The maintenance mechanism unit 12 performs cleaning of the ejection surface of the recording head 20, capping, ejection of unnecessary ink, and the like to discharge unnecessary ink from the recording head 20 and maintain the reliability of the recording head 20. Yes.

  The image forming apparatus 1 is provided with a cover 13 that can open and close a conveyance portion of the recording medium P. When the image forming apparatus 1 is maintained or when a jam occurs, the cover 13 is opened so that the inside of the main body housing 2 can be opened. Maintenance work and removal of the recording medium P in which a jam has occurred can be performed.

  As shown in FIG. 2, the carriage 6 is mounted with recording heads 20y, 20m, 20c, and 20k (arranged as shown in FIG. 3 in this embodiment), and the recording heads 20y, 20m, Reference numerals 20c and 20k are connected to the corresponding color cartridges of the cartridge unit 11 by pipes, and respectively discharge the corresponding color inks to the opposed recording medium P. That is, the recording head 20y is yellow (Y) ink, the recording head 20m is magenta (M) ink, the recording head 20c is cyan (C) ink, and the recording head 20k is black (K) ink. Discharge each.

  The recording head 20 is mounted on the carriage 6 so that its ejection surface (nozzle surface) faces downward (recording medium P side) in FIG. 1, and ejects ink onto the recording medium P.

  In the image forming apparatus 1, an encoder sheet 15 is disposed in parallel with the timing belt 7, that is, the main guide rod 4 over at least the movement range of the carriage 6, and the carriage 6 is an encoder that reads the encoder sheet 15. A sensor 21 is attached. The image forming apparatus 1 controls the movement of the carriage 6 in the main scanning direction by controlling the driving of the main scanning motor 10 based on the reading result of the encoder sheet 15 by the encoder sensor 21.

  As shown in FIG. 3, the recording head 20 mounted on the carriage 6 is composed of a plurality of nozzle rows, each of the recording heads 20y, 20m, 20c, and 20k. An image is formed on the recording medium P by ejecting ink from the nozzle rows onto the recording medium P. In the image forming apparatus 1, an upstream recording head 20 and a downstream recording head 20 are mounted on the carriage 6 in order to ensure a wide width of an image that can be formed on the recording medium P by one scan of the carriage 6. doing. The recording head 20k that discharges black ink is mounted on the carriage 6 twice as many as the recording heads 20y, 20m, and 20c that discharge color ink in order to improve the black printing speed. Further, the recording heads 20y and 20m are arranged adjacent to each other in the main scanning direction so that the colors are aligned in the reciprocating operation of the carriage 6 so that the color does not change between the forward path and the backward path. Therefore, the arrangement of the recording heads 20y, 20m, 20c, and 20k of the recording head 20 is not limited to the arrangement shown in FIG. An arrow B shown in FIG. 3 indicates the sub-scanning direction.

  As shown in FIG. 2, an imaging unit 30 is attached to the carriage 6, and the imaging unit 30 images a subject in order to measure a subject (colorimetric object) during color adjustment processing described later. To do.

  As shown in FIG. 4, the imaging unit (imaging unit) 30 includes a light source 32 and a light receiving element unit 33 mounted on a printed circuit board 31 fixed to the carriage 6.

  The light source 32 uses, for example, an LED (Light Emitting Diode), and irradiates the subject, for example, the colorimetric adjustment color patch CP recorded and output on the recording medium P with the reading light, and the reflected light (diffuse reflection). Light or specularly reflected light) is incident on the light receiving element portion 33. As shown in FIG. 5, four light sources 32 are arranged so as to surround the colorimetric adjustment color patch CP formed on the recording medium P, and the colorimetric adjustment color patch CP is irradiated with uniform reading light. To do.

  The light receiving element unit 33 includes a two-dimensional image sensor 34 such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor, and a lens 35. The light receiving element unit 33 causes the reflected light of the reading light emitted from the light source 32 to the colorimetric adjustment color patch CP to enter the two-dimensional image sensor 34 through the lens 35, and the two-dimensional image sensor 34 outputs image data.

  The imaging unit 30 photoelectrically converts reflected light reflected by the colorimetric adjustment color patch CP, which is emitted from the light source 32 onto a subject such as the colorimetric adjustment color patch CP, by the light receiving element unit 33, which will be described later. As described above, VDATA and control signals (HREE, VSYNC) are output in synchronization with the clock.

  Further, in the image forming apparatus Gk, a nozzle state detection unit 40 as shown in FIGS. 6 to 8 is disposed at a nozzle clogging elimination operation position where the maintenance mechanism unit 12 shown in FIG. 1 is provided.

  A nozzle state detection unit (image loss detection unit) 40 sandwiches a waste liquid tank 12a provided at a position for discharging ink when the nozzle clogging of the maintenance mechanism unit 12 is eliminated, and a light emitting unit (light emitting unit) 41 and a light receiving unit ( Light receiving means) 42 is provided. The nozzle state detection unit 40 discharges from the nozzles of the recording heads 20y, 20m, 20c, and 20k mounted on the carriage 6 that has moved in the main scanning direction to a position just above the waste liquid tank 12a toward the waste liquid tank 12a. The presence / absence, direction, and amount of ink to be used are detected. That is, the light emitting unit 41 of the nozzle state detection unit 40 includes a light emitting element 41a such as an LD (Laser Diode), a collimating lens 41b, an aperture 41c, and the like, and the light receiving unit 42 includes a PD (Photodiode: photodiode). ) Etc. are used. The light emitting unit 41 converts the emitted light from the LD 41a into parallel light by the collimator lens 41b, shapes the detection light with a desired width with respect to the main scanning direction by the aperture 41c, and emits it in the main scanning direction. The light receiving unit 42 is arranged in a state shifted from the position in the main scanning direction with respect to the light emitting unit 41 in the sub scanning direction with respect to the width of the detection light, and as shown in FIG. 8, the recording heads 20y to 20k. The irregularly reflected light that is irregularly reflected by the ink droplets ejected from each nozzle is incident. When the irregularly reflected light is incident, the light receiving unit 42 outputs a detection signal So having a value corresponding to the amount of incident light. That is, in the nozzle state detection unit 40, the light receiving unit 42 detects irregularly reflected light in which the detection light emitted from the light emitting unit 41 in the main scanning direction is irregularly reflected by the ink droplets emitted from the nozzles of the recording heads 20y to 20k. And a so-called scattered light detection type nozzle state detection unit that outputs a detection signal So.

  The image forming apparatus 1 has a block configuration as shown in FIG. 9, and includes a CPU 51, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, a nonvolatile memory 54, a main scanning driver 55, and a recording head. A driver 56, a paper transport unit 57, a sub-scan driver 58, and the like are provided. The carriage 6 includes the recording head 20, the encoder sensor 21, the imaging unit 30, and the like, and a camera controller 60.

  The ROM 52 stores a basic program, a colorimetry program, a color adjustment program, and other necessary system data as the image forming apparatus 1.

  The CPU 51 executes basic processing as the image forming apparatus 1 by controlling each part of the image forming apparatus 1 while using the RAM 53 as a work memory based on a program in the ROM 52. Further, based on the color measurement program and the color adjustment program in the ROM 52, the CPU 51 performs color adjustment for color adjustment based on the RGB values captured by the imaging unit 30 even when there is an illegal image as a part of the color measurement target. A value is obtained, and color adjustment processing during image formation is accurately executed based on the colorimetric value. The CPU 51 controls the movement of the carriage 6 in the main scanning direction by controlling the driving of the main scanning driver 55 based on the encoder value from the encoder sensor 21 in the control of the carriage 6 and the paper transport unit 57. Further, the CPU 51 controls driving of a paper transport unit 57 such as a sub-scan motor and a transport roller (not shown) via the sub-scan driver 58. Further, the CPU 51 controls the ink ejection timing and the ink ejection amount by the recording head 20 via the recording head driver 56. Further, the CPU 51 controls the LED driver 47 to control the lighting drive of the imaging unit 30.

  Further, the CPU 51 receives a detection signal So that detects the nozzle state of each of the recording heads 20y to 20k from the nozzle state detection unit 40, and the nozzle that is the state information of each nozzle of the recording heads 20y to 20k from the detection signal So. Acquire missing information. The CPU 51 stores the acquired nozzle defect information in the nonvolatile memory 54 and transmits it to the camera controller 60. In addition, the CPU 51 acquires the color measurement result captured by the imaging unit 30 from the camera controller 60. Further, the CPU 51 outputs a nozzle missing detection drive signal based on nozzle missing detection pattern data (image defect detection pattern image) to the recording head driver 56 to detect nozzle missing from each nozzle of the recording heads 20y to 20k. Causes the ink droplets to be ejected (for nozzle defect image detection). Further, the CPU 51, when recording and outputting the color measurement adjustment color patch CP, stops the discharge of ink droplets from the defective nozzle and forms the color measurement adjustment color patch CP based on the nozzle defect information. Is output to the recording head driver 56 to cause the recording heads 20y to 20k to form the color measurement adjustment color patch CP corresponding to the nozzle loss on the recording medium P.

  Then, as will be described later, the CPU 51 captures an appropriate colorimetric subject formed on the recording medium P by the recording head 20 serving as an image forming unit over a predetermined imaging range. Colorimetric means for performing colorimetry based on the imaging result of the imaging unit 30 in the effective imaging range, with the range excluding the missing range detected by the nozzle state detection unit 40 as the effective imaging range. Is functioning as

  As described above, the image capturing unit 30 generates a color measurement value for color adjustment that accurately reproduces the color of the image data when the image is recorded and output to the color intended by the user. The patch image PG formed by the recording head 20 on the recording medium P is imaged, and the captured RGB values are output to the CPU 51.

  Further, the CPU 51 determines an image defect state (nozzle defect (defect image)) based on the detection signal So output from the light receiving unit 42 of the nozzle state detection unit 40, and functions as a defect determination unit.

  The camera controller 60 is configured by an FPGA (Field Programmable Gate Array) or the like, and is configured as a block as shown in FIG. The camera controller 60 includes a sub CPU 61, a data storage memory 62, an SRAM (Static Random Access Memory) 63, a PWM (Pulse Width Modulation) controller 64, an I2C (Inter-Integrated Circuit: I square C) controller 65, and a host. A CPU I / F 66, a VIDEO I / F 67, a selection / averaging unit 68, and the like are provided, and each unit is connected by a bus 69. A driver 70 is disposed between the camera controller 60 and the light source 32 of the imaging unit 30. The camera controller 60 controls the imaging unit 30, particularly the photographing operation, automatic exposure (AE) operation, automatic white balance (AWB) adjustment operation, AF operation, display, and the like in the two-dimensional image sensor 34, and various controls. Analog information is grasped using a built-in A / D converter (ADC) as one of information input means.

  When detecting a missing state of an image based on the imaging result of the imaging unit 30, the sub CPU 61 uses the SRAM 63 as a work memory based on a program in the ROM 52, and the two-dimensional image sensor of the imaging unit 30. The defective nozzle is specified by performing a matrix operation to be described later on the image data sent from 34. Therefore, the sub CPU 61 functions as a missing image determination unit that causes the image defect detection pattern image to be captured by the image capturing unit 30 and detects the image defect state based on the pattern image data output from the image capturing unit 30. Yes. In this case, the CPU 51 causes the recording head 20 to form a predetermined image defect detection pattern image on the recording medium P, and functions as a pattern image formation control unit.

  The VIDEO I / F 67 receives VIDEO DATA (VDATA) and control signals (HREF, VSYNC) input from the two-dimensional image sensor 34 in synchronization with the clock (PCLK), and outputs them to the selection unit / averaging processing unit 68. To do. Note that VIDEO DATA (VDATA) is appropriately referred to as image data or data in the following description.

  The selection unit / averaging processing unit 68 selects data at a desired position from the received data (VIDEO DATA), and the averaging processing unit averages the selection data. As will be described later, the selection unit / averaging unit 68 deselects the data where the dot missing has occurred in the selection unit if the missing dot due to the missing nozzle has occurred in the data during the color adjustment process. To exclude them from the objects to be averaged by the averaging processing unit.

  The I2C controller 65 sets the register of the two-dimensional image sensor 34 by the I2C controller 65 in accordance with the instruction from the CPU 51 or the sub CPU 61.

  By setting the register so that the I2C controller 65 changes the imaging range by the two-dimensional image sensor 34 based on the nozzle missing information from the CPU 51 or the sub CPU 61, the data where the dot missing has occurred is excluded in advance. Data (VDATA) is output to the camera controller 67.

  The PWM controller 64 controls the light emission intensity of the LED that is the light source 32 of the imaging unit 30 by changing the PWM duty ratio of the drive signal to the driver 70.

  The data storage memory 62 stores the data average value averaged by the selection unit / average processing unit 68 and the calculation result calculated by the sub CPU 61.

  The host CPU I / F 66 transmits data stored in the data storage memory 62 to the CPU 51 and receives parameters related to control in the camera controller 60 such as nozzle missing data from the CPU 51.

  Then, the CPU 51 uses the colorimetric values of a plurality of color patches (reference color patch KP: see FIG. 11) stored in advance in the nonvolatile memory (reference value storage means) 44 and the two-dimensional image sensor 34 of the imaging unit 30. The RGB values obtained by imaging the reference color patch KP are associated with each other and stored in the memory table Tb1 (see FIG. 11) of the nonvolatile memory 54, and the first linear transformation matrix obtained from the memory table Tb1 is stored in the nonvolatile memory. 54. Further, the CPU 51 converts the colorimetric target RGB value obtained by the colorimetric adjustment patch CP (see FIG. 12) by the two-dimensional image sensor 34 of the imaging unit 30 into the first colorimetric value in the colorimetric space using the first linear conversion matrix. An adjacent point table for selecting a patch at a nearby point that is close to the first colorimetric value from among the colorimetric values of a plurality of color patches, and imaging that is paired with the selected first colorimetric value at the neighboring point A second linear conversion matrix for selecting a reference RGB value and converting the imaging reference RGB value and the reference colorimetric value is calculated and stored in the nonvolatile memory 54, and the reference colorimetric value table, the first conversion matrix, Using the neighborhood point table and the second linear conversion matrix, the RGB values of the colorimetric adjustment color patch CP are converted into colorimetric values.

  That is, the image forming apparatus 1 includes a ROM, an EEPROM (Electrically Erasable and Programmable Read Only Memory), an EPROM, a flash memory, a flexible disk, a CD-ROM (Compact Disc Read Only Memory), a CD-RW (Compact Disc Rewritable), a DVD. A color measurement program for executing the color measurement method of the present invention recorded on a computer-readable recording medium such as a (Digital Versatile Disk), an SD (Secure Digital) card, or an MO (Magneto-Optical Disc) is read. A colorimetric device that implements a colorimetric method that realizes color reproducibility by accurately performing colorimetry even when there is an illegal image in a part of the colorimetric object described later by being introduced into the ROM 52 or the nonvolatile memory 54. It is constructed as an image forming apparatus 1 provided with. This color measurement program is a computer-executable program written in a legacy programming language such as assembler, C, C ++, C #, Java (registered trademark) or an object-oriented programming language, and is stored in the recording medium. And can be distributed. That is, the imaging unit 30, the CPU 51, and the nonvolatile memory 54 function as a color measuring device as a whole.

  Next, the operation of this embodiment will be described. The image forming apparatus 1 according to the present exemplary embodiment accurately performs color measurement even when there is an illegal image as a part of the color measurement target.

  As shown in FIG. 11, the image forming apparatus 1 according to the present exemplary embodiment performs color measurement as a color measurement result of a plurality of reference color patches KP arranged and formed on a reference sheet KS by a spectroscope (color measurement device) BS. At least one of the Lab value and the XYZ value (both the Lab value and the XYZ value in FIG. 11) is stored in the memory table Tb1 of the nonvolatile memory 54 corresponding to the patch number. That is, since the Lab value and the XYZ value can be converted into each other using a known conversion formula, the other can be obtained by storing one in the nonvolatile memory 54, but both are nonvolatile. When stored in the volatile memory 54, the conversion process can be omitted and the processing speed can be improved. In the following description, the Lab value or / and the XYZ value of the reference patch of the reference sheet KS is referred to as a reference colorimetric value as appropriate.

  When the reference colorimetric value is stored in the nonvolatile memory 54 in the memory table Tb1 and the image forming apparatus 1 is in the initial state due to manufacturing or overfall, the image forming apparatus 1 KS is set on the platen 14 of the image forming apparatus 1, the movement of the carriage 6 is controlled, and the same reference color patch KP as that read by the spectroscope BS of the reference sheet KS is read by the imaging unit 30. When the image forming unit 30 reads the reference color patch KP of the reference sheet KS with the image capturing unit 30, the image forming apparatus 1 captures the image capturing reference RGB value which is the RGB value digitally converted by the A / D converter (ADC), that is, device dependent. As shown in FIG. 11, the signal is stored in the memory table Tb1 of the nonvolatile memory 54 in correspondence with the patch number, that is, in correspondence with the reference colorimetric value.

  When the image forming apparatus 1 stores the reference colorimetric value and the imaging reference RGB value in the nonvolatile memory 54, the CPU 51 sets a pair of the XYZ value of the reference colorimetric value and the imaging reference RGB value stored in the nonvolatile memory 54. In other words, a first linear conversion matrix (reference value linear conversion matrix) that is mutually converted is calculated for a pair of XYZ values and imaging reference RGB values of the same patch number, and the calculated first linear conversion matrix is nonvolatile. Stored in the memory 54.

  In the image forming apparatus 1, the above processing is executed in the initial state of the image forming apparatus 1, and after the reference colorimetric values and the imaging reference RGB values as the execution results are registered in the memory table Tb 1 of the nonvolatile memory 54, One linear transformation matrix is calculated and stored in the nonvolatile memory 54.

  In this state, in the image forming apparatus 1, the CPU 51 performs main scanning movement control of the carriage 6, conveyance control of the recording medium P by the paper conveyance unit 57, and recording based on externally input image data, print settings, and the like. While controlling the driving of the head 20 to intermittently transport the recording medium P, the ink ejection from the recording heads 20y, 20m, 20c, and 20k of the recording head 20 is controlled, and the image is recorded on the recording medium P. To record output.

  At this time, the amount of ink discharged from the recording heads 20y, 20m, 20c, and 20k may change due to a change over time, etc. When the amount of ink discharged changes, the color of the image intended by the user differs. Since an image is formed with colors, the color reproducibility deteriorates.

  Therefore, the image forming apparatus 1 executes color adjustment processing for obtaining a colorimetric value and performing color adjustment based on the outer tactile sense at a predetermined color adjustment processing timing.

  That is, at the timing of color adjustment processing, the image forming apparatus 1 forms a plurality of color measurement adjustment color patches (color measurement subjects) CP on the recording medium P by the recording head 20 as shown in FIG. Recorded and output as a colorimetric adjustment sheet CS. In this color measurement adjustment sheet CS, a plurality of color measurement adjustment color patches CP, which are color patches for color measurement adjustment, are formed and output by the recording head 20, and output at the color adjustment processing timing of the image forming apparatus 1. A colorimetric adjustment color patch CP reflecting the characteristics, particularly the output characteristics of the recording head 20 is formed. The color patch data of the colorimetric adjustment color patch CP is stored in the nonvolatile memory 54 in advance.

  Then, as will be described later, the image forming apparatus 1 uses the RGB values obtained by imaging the plurality of color measurement adjustment color patches CP of the color measurement adjustment sheet CS as the color measurement target RGB values (color measurement RGB values), and is nonvolatile. Among the reference colorimetric values registered in the memory table Tb1 of the memory 54, a reference colorimetric value (neighboring reference colorimetric value) that is close in distance to the colorimetric value converted to the colorimetric target RGB value. To obtain a colorimetric value for converting the colorimetric object RGB value into the selected neighborhood reference colorimetric value. The image forming apparatus 1 improves the color reproducibility of the image formed by the image forming apparatus 1 by outputting an image by the recording head 20 based on the image data after performing color conversion based on the colorimetric value. Let

  In view of this, the image forming apparatus 1 sets the color measurement adjustment sheet CS on the platen 14 or holds the color measurement adjustment sheet CS on the platen 14 without discharging it when the color measurement adjustment sheet CS is recorded. The plurality of color measurement adjustment color patches CP of the color measurement adjustment sheet CS positioned on the image 14 are imaged by the imaging unit 30 by controlling the movement of the carriage 6. When the image forming device 30 captures the color measurement adjustment color patch CP of the color measurement adjustment sheet CS by the image capturing unit 30, the image forming apparatus 1 uses RGB values digitally converted by an A / D converter (not shown) mounted on the image capturing unit 30. As shown in FIG. 12, the CPU 51 stores a certain colorimetric target RGB value, that is, a device-dependent signal depending on the device, in the nonvolatile memory 54 (step S1). The CPU 51 converts the colorimetric RGB values into the first XYZ values (step S3) using the first linear conversion matrix (step S2) and stores them in the nonvolatile memory 54 (step S4). For example, in FIG. 12, the CPU 51 converts the colorimetric target RGB values (3, 200, 5) of the imaging unit 30 into the first XYZ values (first colorimetric values) of (20, 80, 10), It is stored in the nonvolatile memory 54.

  The CPU 51 converts the first XYZ value into a first Lab value (first colorimetric value) with reference to the memory table Tb1 of the nonvolatile memory 54 or using a known conversion formula (step S5). It stores in the non-volatile memory 54 (step S6). For example, in FIG. 12, the CPU 51 converts the first XYZ value (20, 80, 10) into the first Lab value (75, −60, 8) that is the imaged colorimetric value.

  Next, the CPU 51 searches for a reference colorimetric value (Lab value) of a plurality of color patches in the memory table Tb1 stored in the non-volatile memory 54, as indicated by the Lab space in FIG. Among the colorimetric values (Lab values), a set of color patches (neighboring color patches) that are close in distance to the first Lab value in the Lab space is selected (step S7). For example, in the Lab space diagram of FIG. 12, 60 color patches are selected and plotted on the Lab space. For example, the CPU 51 calculates the distance between the first Lab value and all the points in the reference colorimetric values (Lab values) of a plurality of color patches as a method for selecting a patch having a close distance. A method of selecting a reference Lab value (a reference Lab value that is hatched in FIG. 12) of a color patch that is close to a certain first Lab value is used.

  Next, as shown in FIG. 13, the CPU 51 refers to the memory table Tb1 and sets the imaging reference RGB value paired with the first Lab value of the selected set, that is, the same patch number as the first Lab of the selected set. A combination of the imaging reference RGB value (selected RGB value) and the reference XYZ value is selected (step S8). The CPU 51 obtains a second linear transformation matrix to be converted between the imaging reference RGB and reference XYZ pairs of the selected combination (selected set) using the least square method, and the obtained second linear transformation matrix is nonvolatile. Stored in the memory 54 (step S9).

  The CPU 51 captures the colorimetric RGB values obtained by imaging each colorimetry adjustment color patch CP of the colorimetry adjustment sheet CS, which is the colorimetry target, with the imaging unit 30 and digitally converting it with the A / D converter. Is used to determine the second XYZ value, which is the second colorimetric value (step S10). The CPU 51 converts the second XYZ value into a second Lab value using a known conversion formula (step S11), and obtains it as a final colorimetric value (step S12).

  The CPU 51 adjusts the image based on the color-converted image data using the obtained colorimetric values, and drives the recording head 20 to form an image based on the image-adjusted image data.

  In other words, the image forming apparatus 1 according to the present embodiment captures and acquires a plurality of color measurement adjustment color patches CP of the color measurement adjustment sheet CS reflecting the output characteristics of the recording head 20 at the color adjustment processing timing. The first Lab value obtained when the reference sheet KS is imaged in the initial state using the first linear transformation matrix as the colorimetric object RGB values is obtained, and the reference Lab of the plurality of color patches registered in the memory table Tb1 is obtained. A pair of patches with a reference Lab value that is close to the first Lab value in the Lab space is selected, and the colorimetric object RGB values corresponding to the selected reference Lab value are selected using the second linear transformation matrix. Lab colorimetric values are obtained by converting them into Lab values. Then, the CPU 51 adjusts the image based on the image data subjected to color conversion using the obtained colorimetric value, and drives the recording head 20 based on the image data subjected to the image adjustment to form an image.

  However, when forming the colorimetric adjustment color patch CP, the nozzles of the recording heads 20y to 20k are clogged, the ejection amount is extremely small, or the ejection direction is bent abnormally. If an abnormality (hereinafter referred to as “nozzle deficiency”) occurs, if the color adjustment process is performed as it is, an accurate colorimetric value cannot be obtained, and the accuracy of color adjustment cannot be ensured.

  Therefore, the image forming apparatus 1 according to the present exemplary embodiment determines whether or not the nozzles of the recording heads 20y to 20k are defective at least at any timing before and after the color adjustment process. That is, nozzle state detection processing (image loss state detection processing) for inspecting whether or not there is a defect in the formed image is performed. Then, the image forming apparatus 1 performs color adjustment by excluding at least the color measurement adjustment color patch CP formed by the missing nozzle from the color measurement adjustment value.

  In this nozzle state detection process, the image forming apparatus 1 moves the carriage 6 to the position of the adjustment mechanism 12 under the control of the CPU 51. The CPU 51 discharges ink droplets from the nozzles of the recording heads 20y to 20k in an appropriate order and in an appropriate number to the waste liquid tank 12a via the recording head driver 56, and controls the operation of the nozzle state detection unit 40. Then, the presence / absence state of the nozzle defect is detected. That is, in the nozzle state detection unit 40, as shown in FIGS. 6 to 8, the light emitting unit 41 emits detection light toward the ink droplets ejected from the nozzle, and the irregularly reflected light irregularly reflected by the ink droplets. The light is incident on the light receiving unit 42. The light receiving unit 42 outputs a detection signal So corresponding to the amount of incident light to the CPU 51.

  The CPU 51 detects and detects which nozzle is defective among the nozzles of the recording heads 20y to 20k based on the drive nozzles of the recording heads 20y to 20k and the detection signal So via the recording head driver 56. The nozzle defect information is stored in the nonvolatile memory 54.

  Then, the CPU 51 passes the nozzle defect information detected and stored in the nonvolatile memory 54 to the camera controller 60.

  The camera controller 60 stores the nozzle defect information received from the CPU 51 in the data storage memory 62 and uses it for data processing in color adjustment processing.

  That is, during the color adjustment process, the camera controller 60 reads the nozzle defect information from the data storage memory 62, excludes it from the target of the color measurement target RGB value based on the color measurement adjustment color patch CP, and acquires the color measurement value. Do.

  For example, the image forming apparatus 1 forms the colorimetric adjustment color patch CP on the recording medium P based on the color patch data by the recording heads 20y to 20k. For example, it is formed as shown in FIG. FIG. 14 shows a case where a square colorimetric adjustment color patch CP of N pixels (pixels) is formed. In the colorimetric adjustment color patch CP, when there is a nozzle defect, for example, as shown in FIG. 15, dot missing (image defect) occurs in the main scanning direction.

  Based on this nozzle defect information (image defect information), the camera controller 60 excludes the color measurement target RGB value based on the color measurement adjustment color patch CP and acquires the color measurement value. As a method of excluding the colorimetric target RGB value from the camera controller 60, for example, the selection unit / averaging processing unit 68 uses the selection unit to perform nozzle missing from data (VDATA) from the two-dimensional image sensor 34. Control is performed so that dot data from the nozzle corresponding to the information (data of a missing dot) is not selected. The selection unit / average processing unit 68 averages the remaining data excluded by the selection unit using the averaging processing unit. That is, the selection unit / averaging processing unit 68 deselects dot data with missing dots by the selection unit and excludes it from the averaging target by the averaging processing unit.

  In addition, the camera controller 60 sets the register so that the I2C controller 65 changes the imaging range of the two-dimensional image sensor 34 based on the nozzle defect information, and excludes data where the nozzle defect has occurred in advance. (VDATA) may be output to the VIDEO I / F 67.

  When the camera controller 60 deselects data (missing data) with missing dots (image loss) by any of the methods described above, for example, in FIG. To do. As described above, the camera controller 60 uses the missing nozzle information (missing state) indicating the missing dot position, the color patch data of the colorimetric adjustment color patch CP, and the nozzle numbers of the recording heads 20y to 20k ( No) is obtained from the relationship.

  Further, the camera controller 60 ejects the colorimetric adjustment color patch CP from the nozzles of two or more nozzles, for example, from the nozzles of the cyan recording head 20c and the yellow recording head 20y shown in FIG. Then, a colorimetric adjustment color patch CP as shown in FIG. 17 is recorded. In such a case, if a plurality of nozzles of the cyan recording head 20c and the yellow recording head 20y are defective, as shown in FIG. The patch CP will be formed. In the case of FIG. 17, the line L1 is a yellow line with a defect in the cyan nozzle, and the line L2 is a cyan line with a defect in the yellow nozzle. The line L3 is a white line with defects in both the cyan and yellow nozzles. In such a case, the camera controller 60 needs to exclude all the lines L1, L2, and L3 from the color measurement target. Therefore, when forming a colorimetric pattern with a plurality of nozzle rows, the camera controller 60 takes OR (OR) for the nozzle loss in each nozzle row and excludes the data due to the nozzle loss from the color measurement target.

  Further, when the image forming apparatus 1 forms an image by the interlace method, as shown in FIG. 18, the image forming apparatus 1 scans a plurality of times (four times in FIG. 18) to obtain the colorimetric adjustment color patch CP. In the nozzle of the black recording head 20k shown in FIG. 18, even if one nozzle has a nozzle defect, a plurality (four) of missing dots (streaks) occur in the colorimetric adjustment color patch CP. .

  Even in such a case, as described above, the camera controller 60 associates the defective nozzle with the line of the imaging range from the relationship between the colorimetric adjustment color patch CP and the nozzle number (No), and the image formed by the defective nozzle. Are excluded from the colorimetric targets.

  As described above, as shown in FIG. 19A, when the data of the image formed by the defective nozzle is excluded from the colorimetric object, the amount of data to be averaged is reduced by the excluded amount. . For example, if 5 frames are captured per patch, the image is excluded from the averaging process by ΔM × N × 5 (pixels), which is 5 times. However, in order to cancel the influence of noise, it is desirable to average as many pixels as possible.

  Therefore, as shown in FIG. 19B, the camera controller 60 increases the number of frames per patch when the nozzle defect occurs, or a position where the nozzle defect does not occur in the same patch by the number of pixels to be excluded. By adding this data to the colorimetric range, the data amount corresponding to the missing nozzle is replenished.

  That is, the image forming apparatus 1 performs the nozzle state detection process as shown in FIG. First, under the control of the CPU 51, the image forming apparatus 1 performs a nozzle defect detection operation that performs nozzle defect detection using the nozzle state detection unit 40 (step S101). When the CPU 51 performs the nozzle defect detection operation and acquires the nozzle defect information, the CPU 51 notifies the camera controller 60 of the nozzle defect information (step S102).

  The camera controller 60 stores the notified nozzle defect information in the data storage memory 62, controls the colorimetric object using the nozzle defect information, and performs colorimetry by excluding data due to the nozzle defect. Then, color adjustment is performed (step S103).

  As a method of excluding the data due to the nozzle defect from the colorimetric object, the camera controller 60 uses the method in which the selection unit / averaging process unit 68 excludes the corresponding data from the object of the averaging process as described above. The I2C controller 65 causes the register of the two-dimensional image sensor 34 to read only the normal range (effective imaging range) in which the data area due to the nozzle defect is excluded from the imaging range, and only the data in the normal range (effective imaging range) is data ( VDATA) is used.

  In the above description, the nozzle defect is detected based on the detection result of the nozzle state detection unit 40, but the method of detecting the nozzle defect (image defect state) is not limited to the above method. For example, in the color adjustment process or before performing color adjustment, ink droplets are ejected from the nozzles of the recording heads 20y to 20k, and a nozzle defect detection pattern (image defect detection pattern image: The nozzle defect may be detected by forming the nozzle defect detection pattern with the imaging unit 30 (see FIG. 21).

  In this case, for example, as shown in FIG. 21, if the recording heads 20y to 20k are provided with 192 nozzles in the sub-scanning direction for each color, the ink is ejected from a defective nozzle at a position indicated by a small circle in FIG. A nozzle defect detection pattern Pn is formed by an image formed by ink droplets and an image formed by ink droplets ejected from normal nozzles other than the defective nozzles at positions indicated by large circles in FIG. In this case, the CPU 51 discharges the first row with the first nozzle so that the ink ejected from the adjacent nozzles does not overlap on the recording medium P, and then the first row and the second row do not overlap. Then, the carriage is moved, and the second row is ejected from the nozzle that was not ejected earlier. The above-described ejection method is applied to ejection of all color inks, and ink droplets are ejected to form a nozzle defect detection pattern Pn having an isolated point pattern as shown in FIG.

  The image forming apparatus 1 detects the nozzle defect (nozzle missing) state by imaging the nozzle defect detection pattern Pn formed on the recording medium P as described above with the imaging unit 30.

  In this case, in the case of FIG. 21, one color is 96 nozzles and the nozzle defect detection pattern Pn is formed in two rows, but 64 nozzles are formed depending on the ink droplet size, the size of the recording medium P, and the like. Nozzle defect detection patterns Pn divided into × 3 rows, 48 nozzles × 4 rows, and so on may be formed.

  The data storage memory 62 stores expected pattern image data when the imaging unit 30 reads a nozzle defect detection pattern in which no nozzle defect exists. The sub CPU 61 compares the pattern image data when the imaging unit 30 reads the nozzle defect detection pattern formed on the recording medium P by the recording head 20 with the expected pattern image data in the data storage memory 62. The presence / absence state of a nozzle defect is detected.

  The image forming apparatus 1 is not limited to the method for forming the nozzle defect detection pattern as a method for detecting the nozzle defect using the imaging unit 30. For example, the presence or absence of a nozzle defect may be detected when the color measurement adjustment color patch CP is imaged by the imaging unit 30.

  In this case, when nozzle defects exist in the nozzles of the recording heads 20y to 20k, for example, a colorimetric adjustment color patch CP with missing dots as shown in FIG. 22A is formed on the recording medium P. . When the colorimetry adjustment color patch CP is read by the imaging unit 30 and the colorimetry range (imaging range) indicated by the dashed line in the rectangle is read, when the leftmost red colorimetry adjustment color patch CP in FIG. Data as shown in FIG. 22B is output from the two-dimensional image sensor 34 to the camera controller 60. In FIG. 22B, the data in the range R1 ± ΔR1 indicated by the broken line indicates the data distribution of the R component colorimetry result, and the small data distribution on the “255” side indicates the data distribution generated due to the missing nozzle. ing.

  Therefore, the camera controller 60 gives in advance a certain width (ΔR1) from the data of the portion indicated by the broken line in FIG. 22B (R1 in FIG. 22B) for each color of the colorimetric adjustment color patch CP. Data in a predetermined range) is stored in the data storage memory 62 in advance as an expected data value. The selection unit of the selection unit / averaging processing unit 68 compares the data sent from the two-dimensional image sensor 34 with this expected value, determines that the data that deviates greatly is the data due to the nozzle defect, and averages the data. It excludes from the object of the averaging process by a process part.

  When the colorimetric adjustment color patch CP is formed by halftone dots, the camera controller 60 calculates the average value for one line for each RGB and compares the average value of the calculation results with the expected value. It is determined whether there is a nozzle defect.

  In the above description, the accuracy of the color adjustment process is eliminated by excluding the dot area of the color measurement adjustment color patch CP that is ejected from the nozzle determined to be a nozzle defect in the nozzle state detection process from the color measurement target. Has improved.

  However, the nozzle determined to be a nozzle defect in the nozzle state detection process may cause not only nozzle omission but also nozzle bending. When such a nozzle bend occurs, as shown in FIG. 23, not only the line where the nozzle is missing is whitened but also the density of the surrounding lines may be high.

  Therefore, the CPU 51 controls the driving of the recording heads 20y to 20k via the recording head driver 56 so as to stop the ink ejection operation from the nozzles in which the nozzles of the recording heads 20y to 20k are missing.

  In this way, the colorimetric adjustment color patch CP can be formed in a normal state by ink droplets ejected from nozzles other than the nozzle that is nozzle deficient, and the accuracy of color adjustment processing is further improved. be able to.

  As described above, the image forming apparatus 1 according to the present embodiment detects a recording head (image forming unit) 20 that forms images of a plurality of colors on the recording medium P, and a defect state of an image formed by the recording head 20. A nozzle state detection unit 40 or an image loss detection unit constructed by the CPU 51 and the sub CPU 61, and an imaging unit (imaging unit) that captures an image of a colorimetric object formed on the recording medium P by the recording head 20 over a predetermined imaging range. Means) and a range obtained by excluding the defect range detected by the image loss detection means from the imaging range by the imaging unit 30 as an effective imaging range, and measured based on the imaging result by the imaging unit 30 of the effective imaging range. CPU (colorimetric means) 51 for performing color.

  Therefore, even when the subject to be colorimetric formed by the recording head 20 has an image loss state, color measurement can be performed based on the effective imaging range excluding the loss range, and a part of the colorimetry target Even if there is an illegal image, colorimetry can be performed accurately. As a result, the image quality of the formed image can be improved.

  Further, the image forming apparatus 1 of the present embodiment includes an image defect detection processing step for detecting a defect state of the image formed by the recording head 20 that forms an image of a plurality of colors on the recording medium P, and the recording head 20. An imaging process step of imaging a colorimetric object formed on the recording medium P over a predetermined imaging range, and a defect detected in the image defect detection processing step in the imaging range in the imaging process step A color measurement method including a color measurement process step of performing color measurement based on an image pickup result in the image pickup processing step of the effective image pickup range with a range excluding the range as an effective image pickup range is executed.

  Therefore, even when the subject to be colorimetric formed by the recording head 20 has an image loss state, color measurement can be performed based on the effective imaging range excluding the loss range, and a part of the colorimetry target Even if there is an illegal image, colorimetry can be performed accurately.

  Furthermore, the image forming apparatus 1 according to the present embodiment detects an image defect detection that detects a defect state of the image formed by the recording head 20 that forms an image of a plurality of colors on the recording medium P in a control processor such as the CPU 51. Processing, imaging processing for imaging a colorimetric object formed on the recording medium P by the recording head 20 over a predetermined imaging range, and detection by the image loss detection processing among the imaging ranges in the imaging processing A colorimetry program for executing a colorimetry process for performing a colorimetry based on the imaging result of the imaging process of the effective imaging range, with the range excluding the missing area as an effective imaging range, is installed.

  Therefore, even when the subject to be colorimetric formed by the recording head 20 has an image loss state, color measurement can be performed based on the effective imaging range excluding the loss range, and a part of the colorimetry target Even if there is an illegal image, colorimetry can be performed accurately.

  The image forming apparatus 1 according to the present exemplary embodiment is the recording head 20 in which the image forming unit includes a plurality of nozzles and forms an image by ejecting ink droplets from the nozzles. , A light emitting unit (light emitting means) 41 for emitting detection light toward the ink droplets ejected from each nozzle of the recording head 20, and a detection signal corresponding to the amount of light received by receiving scattered light of the detection light from the ink droplets A light receiving unit (light receiving unit) 42 for outputting, and a CPU (deletion determining unit) 51 for determining a missing state of an image based on a detection signal output from the light receiving unit 42 are provided.

  Therefore, it is possible to detect the ejection state of the ink droplets from each nozzle of the recording head 20 at a low cost and accurately, and to detect the image defect state at a low cost and accurately.

  Furthermore, in the image forming apparatus 1 of the present embodiment, the image defect detection unit causes the recording head 20 to form a predetermined nozzle defect detection pattern (image defect detection pattern image) on the recording medium P (a pattern image). Formation control means) 51 and a sub CPU (defect image determination means) for causing the image pickup unit 30 to pick up the nozzle defect detection pattern and determining the image defect state based on the pattern image data output from the image pickup unit 30. 61.

  Therefore, it is possible to detect a nozzle defect (defect image) without providing the nozzle state detection unit 40, and to perform color measurement inexpensively and accurately even when there is an illegal image in a part of the color measurement target. it can.

  Further, in the image forming apparatus 1 according to the present embodiment, the sub CPU 61 as the missing image determination unit stores the pattern image data output from the imaging unit 30 when the nozzle defect detection pattern is imaged and the data storage memory 62 in advance. It compares the expected pattern image data obtained when the image capturing unit 30 captures the stored nozzle defect detection pattern having no defect, and determines the image defect state.

  Therefore, it is possible to detect a nozzle defect (defect image) inexpensively and quickly without providing the nozzle state detection unit 40, and even when there is an illegal image in a part of the colorimetric object, the colorimetry is inexpensive and accurate. Can be done.

  Furthermore, in the image forming apparatus 1 according to the present embodiment, the image loss detection unit uses the color measurement adjustment color patch CP that is the subject of the color measurement target formed by the recording head 20 at the color measurement timing. A pattern image may be picked up by the image pickup unit 30 and the image defect state may be detected based on the pattern image data output from the image pickup unit 30.

  In this way, it is not necessary to form a nozzle defect detection pattern in order to detect the nozzle defect, and the nozzle defect (defect image) can be detected more quickly and inexpensively. Even if there is an illegal image in the part, the color measurement can be performed more inexpensively and promptly.

  Further, the CPU 51 as the color measurement unit performs the color measurement by complementing the missing range excluded from the imaging range by the imaging unit 30 with the data of the effective imaging range.

  Therefore, it is possible to prevent a decrease in colorimetric accuracy due to a decrease in the number of data in the predation process, and it is possible to perform colorimetry more accurately.

  In the image forming apparatus 1 according to the present embodiment, when the CPU 51 forms an image with the recording head 20 after color measurement, a part of the recording head 20 that forms an image in which a defect is detected by the image defect detection unit. The recording head 20, that is, the formation of an image by the nozzle in which the discharge curve or the like is generated is prohibited.

  Therefore, color measurement can be performed accurately and the image quality of the formed image can be improved.

  24 to 38 are diagrams showing a second embodiment of the image forming apparatus, colorimetric method, and colorimetric program of the present invention. FIG. 24 is an image forming apparatus, colorimetric method, and colorimetric program of the present invention. It is a top view of the imaging part 100 of the image forming apparatus to which 2nd Example of this is applied.

  The present embodiment is applied to an image forming apparatus similar to the image forming apparatus 1 shown in FIG. 1 of the first embodiment, and although not shown in the description of the present embodiment, FIG. Similar components will be described using the same reference numerals used in the first embodiment as necessary.

  In the image forming apparatus 1, the imaging unit (imaging means) 100 is shown in FIG. 25, which is a sectional view taken along arrows AA in FIGS. 24 and 24, and FIG. 26, which is a sectional view taken along arrows BB in FIG. As described above, a rectangular box-shaped frame body 102 whose surface on the substrate 101 side is open is fixed to the substrate 101 by a fastening member 103, and the substrate 101 is fixed to the carriage 6 shown in FIG. ing.

  The imaging unit 100 is provided with an image sensor unit 104 at the center of the surface of the substrate 101 on the frame body 102 side. The image sensor unit 104 is a CCD (Charge Coupled Device) sensor or a CMOS (Complementary). A two-dimensional image sensor 105 such as a metal oxide semiconductor) sensor and a lens 106 are provided. The imaging unit 100 is located on the center line Lo in the sub-scanning direction passing through the center of the image sensor unit 104 and at a position spaced apart from the center of the image sensor unit 104 by a predetermined amount at equal intervals in the sub-scanning direction. In addition, a pair of illumination light sources 107 are mounted, and as the illumination light sources 107, LEDs or the like are used.

  In the imaging unit 100, the lower surface of the surface 102 (hereinafter referred to as a bottom surface) 102 a opposite to the substrate 101 of the frame 102 faces the recording medium P on the platen 14 with a predetermined distance d. In this state, the lower surface portion 102a is formed with a substantially rectangular opening portion 102b and an opening portion 102c in the main scanning direction around the center line Lo. As will be described later, the gap d is preferably small in consideration of the focal length with respect to the two-dimensional image sensor 105, but from the relationship with the flatness of the recording medium P, the lower surface of the frame 102 and the recording medium P are used. Is set to a size such that, for example, 1 mm to 2 mm.

  In the opening 102b, a concave portion 102d having a predetermined width is formed on the surface on the recording medium P side along the periphery of the opening 102b, and the reference chart KC is detachably set in the concave portion 102d. A holding plate 102e that covers the surface of the reference chart KC on the recording medium P side and is held in the recess 102d is detachably attached to the recess 102d of the opening 102b of the frame body 102. The portion 102b is closed by the reference chart KC and the holding plate 102e. The holding plate 102e has a smooth flat surface on the recording medium P side.

  The opening 102c is used to image the reference color patch KP of the reference sheet KS and the colorimetric adjustment color patch CP of the colorimetry adjustment sheet CS, which are imaging objects (subjects) formed on the recording medium P. It is done. The opening 102c may be at least large enough to capture all images to be imaged. However, since there is a gap d between the frame 102 and the imaging object, a shadow that occurs around the opening 102c is generated. Considering this, it is formed in an opening state that is slightly larger than the size of the imaging region to be imaged.

  The reference chart KC is compared with the reference color patch KP of the reference sheet KS and the imaged colorimetric value of the colorimetric adjustment color patch CP of the colorimetric adjustment sheet CS that is the image pickup object in the color adjustment process. The image is taken together with the reference color patch KP and the colorimetric adjustment color patch CP. That is, the imaging unit 100 includes the reference color patch KP of the reference sheet KS and the colorimetric adjustment color patch CP of the colorimetry adjustment sheet CS that are outside the frame 102 through the opening 102c provided in the lower surface part 102a of the frame 102. In addition, the color patch on the reference chart KC attached to the recess 102d formed around the opening 102b of the lower surface portion 102a of the frame 102 is imaged as a comparison target. Note that since the two-dimensional image sensor 105 sequentially scans the pixels and reads the image, the imaging unit 100 sequentially reads the reference color patch KP of the reference sheet KS, the color measurement adjustment patch CP of the color measurement adjustment sheet CS, and the reference chart KC. In this case, images of the reference color patch KP, the colorimetric adjustment patch CP, and the reference chart KC are acquired within one frame.

  As shown in FIG. 27, the reference chart KC has a plurality of reference color patch rows Pa to Pd and dot diameters for color measurement on the inner surface (upper surface) of the frame body 102 as shown in FIG. A measurement pattern row Pe, a distance measurement line lk, and a chart position specifying marker mk are formed.

  The color measurement patch rows Pa to Pd include a patch row Pa in which YMC primary color patches are arranged in gradation order, a patch row Pa in which RGB secondary color patches are arranged in gradation order, and a gray color. There are a patch array (achromatic gradation pattern) Pc in which patches of a scale are arranged in order of gradation, and a patch array Pd in which patches of a tertiary color are arranged, and the dot diameter measurement pattern array Pe has a size. It is a pattern sequence for measuring a geometric shape in which different circular patterns are arranged in order of size.

  The distance measurement line lk is formed as a rectangular frame surrounding the color measurement patch rows Pa to Pd and the dot diameter measurement pattern row Pe. The chart position specifying markers mk are provided at the positions of the four corners of the distance measuring line lk, and are markers for specifying each patch position.

  The color measurement control unit 120 (see FIG. 29), which will be described later, specifies the distance measurement line lk and the chart position specifying markers mk at the four corners from the image data of the reference chart KC acquired from the imaging unit 100, whereby the reference chart The position of KC and the position of each pattern are specified.

  As shown in FIG. 11, the colorimetric values (Lab values) in the Lab color space, which is the standard color space, are measured in advance for each patch constituting the colorimetric reference color patch rows Pa to Pd using the spectroscope BS. Therefore, the color measurement adjustment color patch CP of the color measurement adjustment sheet CS is a reference value for color measurement. The configuration of the colorimetric patch rows Pa to Pd arranged in the reference chart KC is not limited to the arrangement example shown in FIG. 27, and any patch row can be used. As long as possible, a patch capable of specifying a wide color range may be used, and the YMCK primary color patch row Pa and the gray scale patch row Pc may be used for the ink used in the image forming apparatus 1. It may be composed of patches of colorimetric values. Further, the RGB secondary color patch row Pa of the reference chart KC may be composed of patches of colorimetric values that can be developed with ink used in the image forming apparatus 1, and further, colorimetric values such as JapanColor. May be used.

  Since the reference chart KC is disposed in the recess 102d formed on the outer periphery of the surface on the recording medium P side of the opening 102b formed in the lower surface portion 102a of the frame 102, the recording medium P The image can be picked up by the two-dimensional image sensor 105 of the image sensor unit 104 at the same focal length as the image pickup target.

  Further, the reference chart KC is detachably set in a recess 102d formed on the outer periphery of the surface on the recording medium P side of the opening 102b formed in the lower surface portion 102a of the frame body 102 to be recorded. Since the surface on the medium P side is detachably held by the holding plate 102e that is detachably attached to the concave portion 102d, even if dust or the like entering the frame 102 adheres to the surface of the reference chart KC. Then, after removing the holding plate 102e and the reference chart KC and cleanly cleaning the reference chart KC, it can be attached again, and the measurement accuracy of the reference chart KC can be improved.

  In the imaging unit 100, the optical path length changing member 108 is disposed in the optical path between the recording medium P and the two-dimensional image sensor 105 through the opening 102c in a state where the opening 102c is closed. The changing member 108 is a transmissive member having a refractive index n (n is an arbitrary value). As illustrated in FIG. 25, the optical path length changing member 108 has an outer shape larger than the opening 102 c and is disposed in the frame body 102. The fixing position of the optical path length changing member 108 is not limited to the position of the opening 102c inside the frame 102 as shown in FIG. 25, but may be in the optical path between the opening 102c and the two-dimensional image sensor 105. For example, the position on the imaging surface side of the frame body 102, the position inside the frame body 102 and away from the opening 102, and the like may be used. When the light passes through the optical path length changing member 108 having the refractive index n, the light is extended in accordance with the refractive index n of the optical path length changing member 108, and the two-dimensional image sensor 105 is in a state where the image is lifted. The image floating amount C can be obtained by the following equation (1) when the length of the optical path length changing member 108 is Lp.

C = Lp (1-1 / n) (1)
Further, the focal length L of the focal plane of the imaging unit 100 other than the reference chart KC, that is, the focal length L to the surface of the recording medium P imaged through the optical path length changing member 108 and the opening 102c is expressed by the following equation (2). ).

L = Lc + Lp (1-1 / n) (2)
Here, Lc is the distance between the top of the lens 106 on the imaging target side and the reference chart KC, and n is the refractive index of the optical path length changing member 108.

  Therefore, for example, when the refractive index n of the optical path length changing member 108 is 1.5, L = Lc + Lp (1-1 / 1.5) = Lc + Lp (1/3), and the length of the optical path length changing member 108 The optical path length can be increased by about 1/3 of Lp. If Lp = 9 [mm], L = Lc + 3 [mm], and the imaging position of the reference chart KC and the focal position of the imaging surface of the recording medium P can be matched, and the reference chart KC And the imaging surface of the recording medium P can be set in a conjugate relationship.

  The imaging unit 100 uses illumination light from the same illumination light source 107 for illumination light that irradiates the reference chart KC and illumination light that irradiates the imaging surface of the recording medium P through the optical path length changing member 108 and the opening 102c. It is light, and the reference chart KC and the imaging surface of the recording medium P can be imaged together under the same illumination conditions. In addition, the illumination light source 107 is disposed on the center line Lo that is a substantially intermediate position between the reference chart KC and the recording medium P, and two illumination light sources 107 are disposed on the object on the center line Lo with respect to the lens 106. The imaging area of the reference chart KC and the recording medium P can be illuminated uniformly under substantially the same conditions.

  Further, the imaging unit 100 is arranged in two dimensions because the arrangement condition of the aperture 102c of the imaging region and the reference chart KC is arranged substantially symmetrically with respect to the center line Lo connecting the center of the lens 106 and the illumination light source 107. The imaging conditions of the image sensor 105 can be made line symmetrical and the same, and the accuracy of color adjustment processing and color measurement processing of the two-dimensional image sensor 105 using the reference chart KC can be improved.

  The image forming apparatus 1 according to the present embodiment has a block configuration as shown in FIG. 28. The block configuration of the image forming apparatus 1 according to the first embodiment is that the camera controller is the colorimetric control unit 120. In addition, the imaging unit 100 is different. Therefore, in FIG. 28, the same components as those in FIG. 6 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  As shown in FIG. 28, the image forming apparatus 1 of the present embodiment is similar to the image forming apparatus 1 of the first embodiment in that a CPU 51, a ROM 52, a RAM 53, a nonvolatile memory 54, a main scanning driver 55, and a recording head driver 56 are used. A paper transport unit 57, a sub-scan driver 58, a nozzle state detection unit 40, a recording head 20 mounted on the carriage 6, an encoder sensor 21, and the like, and an imaging unit 100 and a measurement unit mounted on the carriage 6. A color control unit 120 and the like are provided.

  In the image forming apparatus 1 according to the present embodiment, the CPU 51 and the camera controller 60 according to the first embodiment perform the color adjustment process accompanied by the color measurement process. The color measurement control unit 120 performs the color measurement for the color measurement process. The CPU 51 performs color adjustment processing on the image data using the colorimetric values obtained by the color measurement processing, and controls the recording head 20 based on the image data subjected to the color adjustment processing, thereby reproducing the color. An image is formed in a state where the property is improved. Similarly to the first embodiment, the CPU 51 performs a nozzle defect detection process for detecting a defective nozzle based on the detection result of the nozzle state detection unit 40.

  That is, as described above, the imaging unit 100 is arranged inside the color measurement adjustment color patch CP and the frame body 102 formed on the recording medium P by the recording head 20 that changes with time during the color adjustment processing. The image sensor unit 104 captures the obtained reference chart KC and outputs image data obtained by capturing the colorimetric adjustment color patch CP and the reference chart KC to the colorimetry control unit 120. The color measurement control unit 120 uses the color measurement adjustment color patch CP captured by the image sensor unit 104 during the color adjustment processing acquired from the image capture unit 100 as a reference color patch (hereinafter, referred to as a reference color patch) of the reference sheet KS as in the first embodiment. When the image pickup unit 100 reads the initial reference color patch), the initial reference colorimetric value (initial reference Lab value and the color measurement value at the time of initial reference of the patches Pa to Pe of the reference chart KC read and stored is read. After conversion to at least one of the initial reference XYZ values, the colorimetric adjustment process similar to the colorimetric adjustment process in the first embodiment is performed. Therefore, the imaging unit 100 and the colorimetric control unit 120 function as a colorimetric device as a whole.

  The imaging unit 100 and the colorimetric control unit 120 are configured as a block as shown in FIG. The imaging unit 100 includes the image sensor unit 104 and the illumination light source 107, and an image processing unit 110 and an interface unit 111 are mounted on the substrate 101. The image processing unit 110 includes an A / D conversion unit 112. A shading correction unit 113, a white balance correction unit 114, a γ correction unit 115, and an image format conversion unit 116.

  The image processing unit 110 performs necessary image processing on the analog RGB image data that the image sensor unit 104 captures and outputs, and outputs the analog RGB image data to the colorimetry control unit 120.

  The A / D conversion unit 112 digitally converts the analog RGB signal input from the image sensor unit 104 and outputs the converted signal to the shading correction unit 113.

  The shading correction unit 113 corrects an error in image data caused by uneven illumination of illumination light from the illumination light source 107 with respect to the imaging range of the image sensor unit 104 for RGB image data input from the A / D conversion unit 112. And output to the white balance correction unit 114.

  The white balance correction unit 114 corrects the white balance of the RGB image data after the shading correction, and outputs the corrected data to the γ correction unit 115.

  The γ correction unit 115 corrects the image data input from the white balance correction unit 114 so as to compensate for the linearity of sensitivity of the image sensor unit 104 and outputs the corrected data to the image format conversion unit 116.

  The image format conversion unit 116 converts the image data after γ correction into an arbitrary format and outputs the converted data to the colorimetry control unit 120 via the interface unit 111.

  The interface unit 111 is used for the imaging unit 100 to acquire various setting signals, timing signals, and light source driving signals sent from the colorimetry control unit 120, and to send image data from the imaging unit 100 to the colorimetry control unit 120. Interface.

  The color measurement control unit 120 includes a frame memory 121, a timing signal generation unit 122, a light source drive control unit 123, a calculation unit 124, a nonvolatile memory 125, and the like, and the calculation unit 124 includes a color measurement value calculation unit 126. .

  The frame memory 121 is a memory that temporarily stores data (image data) sent from the imaging unit 100, and outputs stored image data to the calculation unit 124.

  As in the nonvolatile memory 54 of the first embodiment, the nonvolatile memory 125 includes a plurality of reference colors arranged on the reference sheet KS by the spectroscope (colorimetry device) BS as shown in FIG. At least one of the Lab value and the XYZ value (both the Lab value and the XYZ value in FIG. 11), which is the colorimetric value of the colorimetric result of the patch KP, is stored in the nonvolatile memory 125 as the reference colorimetric value. It is stored in the table Tb1 corresponding to the patch number. In addition, the non-volatile memory 125 stores nozzle defect information sent from the CPU 51.

  Further, the image forming apparatus 1 stores the reference sheet KS in the image forming apparatus 1 in a state where the reference colorimetric values are stored in the memory table Tb1 of the nonvolatile memory 125 and in the initial state of the image forming apparatus 1. An imaging reference RGB value obtained by setting the same on the platen 14 and controlling the movement of the carriage 6 to read the same reference patch KP as read by the spectroscope BS of the reference sheet KS by the imaging unit 100 is stored in the nonvolatile memory 125. Is stored in correspondence with the patch number, that is, in correspondence with the reference colorimetric value, and each patch of the reference chart KC of the imaging unit 100 is imaged to obtain the RGB value. The RGB value of each patch of the chart KC is set as the initial reference RGB value RdGdBd, and the memory of the nonvolatile memory 125 under the control of the calculation unit 124 It is stored in the Buru Tb1.

  The initial reference RGB value RdGdBd is actually the RGB value of each patch of the reference chart KC imaged when the imaging unit 100 images the reference color patch KP of the reference sheet KS. The number of color patches KP is as large as, for example, several hundred patches. Since the reference color patches KP are imaged in order for each patch, the reference chart KC is also imaged every time the reference color patch KP is imaged. There are a lot of KC image data.

  Therefore, in the image forming apparatus 1 of the present embodiment, the colorimetry control unit 120 averages the RGB values of each patch of the reference chart KC captured by the imaging unit 100 for each predetermined imaging region, for example, for each color of the patch. Then, the average value is stored in the memory table Tb1 of the nonvolatile memory 125 as the initial reference RGB value RdGdBd.

  In this case, the colorimetric control unit 120 is not limited to the average value of the RGB values captured a plurality of times among the RGB values of each patch of the reference chart KC captured by the imaging unit 100 together with the reference sheet KS. For example, an appropriate RGB value such as the RGB value captured first, the RGB value captured at an appropriate number of times, and the median RGB value may be set as the initial reference RGB value RdGdBd.

  In the image forming apparatus 1 of the present embodiment, when the reference colorimetric value, the imaging reference RGB value, and the initial reference RGB value RdGdBd are stored in the nonvolatile memory 125, the colorimetric value calculation unit 126 is the same as in the first embodiment. In addition, the XYZ value of the reference colorimetric value stored in the non-volatile memory 125 and the pair of the imaging reference RGB value, that is, the pair of the XYZ value and the imaging reference RGB value of the same patch number are mutually converted. One linear conversion matrix (reference value linear conversion matrix) is calculated, and the calculated first linear conversion matrix is stored in the nonvolatile memory 125.

  In the image forming apparatus 1, the above processing is executed in the initial state of the image forming apparatus 1, and the reference colorimetric values, imaging reference RGB values, and initial reference RGB values RdGdBd as execution results are stored in the memory table Tb 1 of the nonvolatile memory 125. Then, the first linear transformation matrix is calculated and stored in the nonvolatile memory 125.

  Further, as will be described later, the image forming apparatus 1 according to the present exemplary embodiment includes a colorimetric adjustment color patch CP and a frame body 102 formed on the recording medium P by the recording head 20 that changes with time during color adjustment processing. The image sensor unit 104 captures an image of the reference chart KC arranged inside the image data, and outputs image data including the colorimetric adjustment color patch CP and the reference chart KC to the colorimetry control unit 120. The color measurement control unit 120 uses the color measurement adjustment color patch CP imaged by the image sensor unit 104 during the color adjustment processing acquired from the imaging unit 100 as a reference color patch (hereinafter referred to as an initial reference color patch) of the reference sheet KS. After conversion to the initial reference RGB values RdGdBd of the patches Pa to Pe of the reference chart KC read and stored when read by the imaging unit 100, the color measurement in the first embodiment is performed on the initial reference RGB values RdGdBd. A colorimetric process similar to the process is performed.

  That is, the arithmetic unit 124 controls the operation of the colorimetric control unit 120, and the colorimetric value calculation unit 126 executes the colorimetric processing and outputs the colorimetric value that is the result of the colorimetric processing to the CPU 51. To do.

  Then, the CPU 51 performs color adjustment processing on the image data using the colorimetric values, and controls the recording head 20 based on the color adjustment processed image data, thereby forming an image with improved color reproducibility. To do.

  Further, the colorimetric value calculation unit 126 executes the function of the selection unit of the selection unit / average processing unit 68 of the first embodiment. In other words, the colorimetric value calculation unit 126 excludes the data of the dot area discharged from the defective nozzle based on the nozzle defect information stored in the nonvolatile memory 125 from the data of the imaging unit 100 color, and performs averaging. Process.

  The imaging unit 100 and the color measurement control unit 120 function as a color measurement device as a whole.

  The image forming apparatus 1 of the present embodiment is recorded on a computer-readable recording medium such as a ROM, EEPROM, EPROM, flash memory, flexible disk, CD-ROM, CD-RW, DVD, SD card, MO, and the like. By implementing a color measurement program for executing the color measurement method of this embodiment and introducing it into the ROM 52 or the non-volatile memory 125, the color reproducibility considering the temporal change described later can be realized inexpensively and stably. The image forming apparatus 1 includes a color measurement device that executes a color measurement method for accurately performing color measurement even when there is an illegal image in a part of the color measurement target. This color measurement program is a computer-executable program written in a legacy programming language such as assembler, C, C ++, C #, Java (registered trademark) or an object-oriented programming language, and is stored in the recording medium. And can be distributed.

  Next, the operation of this embodiment will be described. The image forming apparatus 1 according to the present exemplary embodiment realizes color reproducibility in consideration of changes with time at low cost and stably, and accurately performs color measurement even when there is an illegal image in a part of the color measurement target.

  As shown in FIG. 11, the image forming apparatus 1 according to the present embodiment uses the spectroscope (colorimetry device) BS to calculate the color measurement results of the plurality of reference color patches arranged and formed on the reference sheet KS as Lab values. And at least one of the XYZ values is stored as a reference colorimetric value corresponding to the patch number in the memory table Tb1 of the nonvolatile memory 125.

  Further, when the image forming apparatus 1 is in a state where the reference colorimetric values are stored in the nonvolatile memory 125 in the memory table Tb1 and the image forming apparatus 1 is in an initial state due to manufacture, overfall, or the like, The reference sheet KS is set on the platen 14 of the image forming apparatus 1, the movement of the carriage 6 is controlled, and the same reference patch as that read by the spectroscope BS of the reference sheet KS is read by the imaging unit 100. As shown at 30, each patch (initial reference color patch) of the reference chart KC arranged inside the frame 102 is imaged.

  When the image forming apparatus 1 captures the reference patch of the reference sheet KS and each patch of the reference chart KC by the imaging unit 100, the image forming apparatus 1 has RGB values obtained by processing the image data obtained by capturing the reference patch of the reference sheet KS by the image processing unit 110. As shown in FIG. 11, the calculation unit 124 of the colorimetry control unit 120 associates the imaging reference RGB values, that is, device-dependent signals, with the patch numbers in the memory table Tb1 of the nonvolatile memory 125, as shown in FIG. That is, the initial reference RGB value RdGdBd, which is the RGB value obtained by reading the initial reference color patch of the reference chart KC and processing it by the image processing unit 110 while storing it in correspondence with the reference colorimetric value, is shown in FIG. As shown in FIG.

  Note that the calculation unit 124 is provided for each predetermined region, for example, a region (color measurement target region, imaging range) indicated by a broken line in FIG. 30 in the image data of the initial reference color batch of the reference chart KC read by the imaging unit 100. An average value is calculated and set as an initial reference RGB value RdGdBd. When the initial reference RGB value RdGdBd is calculated by averaging a large number of pixels in the colorimetric object region in this way, the influence of noise can be reduced and the bit resolution can be improved. FIG. 31 (b) is a scatter diagram in which the initial reference RGB value RdGdBd is plotted. FIG. 31 (a) is a conversion of the initial reference RGB value RdGdBd into a reference Lab value Ldadbd and an XYZ value converted into Lab values. The reference XYZ value xdydzd also indicates a state registered in the nonvolatile memory 125.

  When the image forming apparatus 1 stores the reference colorimetric value, the imaging reference RGB value, and the initial reference RGB value RdGdBd in the nonvolatile memory 125, the colorimetric value calculation unit 126 of the calculation unit 124 is stored in the nonvolatile memory 125. Calculating a first linear conversion matrix for mutual conversion with respect to a pair of XYZ values and imaging reference RGB values of the reference colorimetric values, that is, a pair of XYZ values and imaging reference RGB values of the same patch number The first linear transformation matrix is stored in the nonvolatile memory 125.

  In this state, in the image forming apparatus 1, the CPU 51 performs main scanning movement control of the carriage 6, conveyance control of the recording medium P by the paper conveyance unit 57, and recording based on externally input image data, print settings, and the like. While controlling the driving of the head 20 to intermittently transport the recording medium P, the ink ejection from the recording heads 20y, 20m, 20c, and 20k of the recording head 20 is controlled, and the image is recorded on the recording medium P. To record output.

  At this time, the amount of ink discharged from the recording heads 20y, 20m, 20c, and 20k may change depending on the characteristics unique to the device, changes with time, and the like. An image is formed with a color different from the color, and the color reproducibility deteriorates.

  Therefore, the image forming apparatus 1 executes color adjustment processing for obtaining a colorimetric value and performing color adjustment based on the colorimetric value at a predetermined color adjustment processing timing.

  That is, when the color adjustment processing timing comes, the image forming apparatus 1 uses a recording head 20 to add a plurality of color patches (colorimetry adjustment color patches) CP as shown in FIG. 32, as in the first embodiment. It is formed on the recording medium P and recorded and output as a colorimetric adjustment sheet CS. In this color measurement adjustment sheet CS, a plurality of color measurement adjustment color patches CP, which are color patches for color measurement adjustment, are formed and output by the recording head 20, and output at the color adjustment processing timing of the image forming apparatus 1. A colorimetric adjustment color patch CP reflecting the characteristics, particularly the output characteristics of the recording head 20 is formed. Note that the color patch data of the color measurement adjustment color patch CP is stored in advance in the nonvolatile memory 125 or the like.

  Then, as will be described later, the image forming apparatus 1 uses the RGB values obtained by imaging the plurality of color measurement adjustment color patches CP of the color measurement adjustment sheet CS as color measurement target RGB values (color measurement RGB values). The color target RGB value is converted into an initial reference RGB value RdGdBd, and the initial reference RGB value of the reference colorimetric values registered in the memory table Tb1 of the non-volatile memory 125 will be hereinafter described in the same manner as in the first embodiment. A colorimetric value for selecting a reference colorimetric value (neighboring reference colorimetric value) close in distance to the colorimetric value obtained by converting RdGdBd and converting the colorimetric target RGB value to the selected neighborhood reference colorimetric value And the image is output by the recording head 20 based on the image data after the color conversion is performed based on the colorimetric value, thereby improving the color reproducibility of the image formed by the image forming apparatus 1.

  Therefore, as shown in FIG. 32, the image forming apparatus 1 sets the colorimetric adjustment sheet CS on the platen 14 or does not eject the colorimetric adjustment sheet CS when it is recorded. As the held state, a plurality of color measurement adjustment color patches CP of the color measurement adjustment sheet CS on the platen 14 are imaged by the imaging unit 100 while controlling the movement of the carriage 6, and at the same time the reference chart KC is captured by the imaging unit 100. Capture the patch.

  When the image forming apparatus 1 captures the color measurement adjustment color patch CP of the color measurement adjustment sheet CS and the patch of the reference chart KC by the image capturing unit 100, the image processing unit 110 of the image capturing unit 100 performs the color measurement of the color measurement adjustment sheet CS. After performing necessary image processing on the image data of the adjustment color patch CP and the image data of the reference chart KC, the image data (RGB value) of the color measurement adjustment color patch CP of the color measurement adjustment sheet CS is measured. The color object RGB values, that is, device-dependent signals depending on the device, and the image data (RGB values) of the patches of the reference chart KC are sent to the color measurement control unit 120 as the color measurement reference RGB values RdsGdsBds. As shown in FIG. 32, the color control unit 120 temporarily stores it in the frame memory 121 (step S21).

  Note that the colorimetric reference RGB value RdsGdsBds is actually the RGB value of each patch of the reference chart KC imaged when the imaging unit 100 images the colorimetric adjustment patch CP of the colorimetry adjustment sheet CS. The number of color measurement adjustment patches CP of the color measurement adjustment sheet CS is as large as, for example, several hundred patches. Since the color measurement adjustment patches CP of the color measurement adjustment sheet CS are captured in order for each patch, the reference chart KC is also color measurement. The image is picked up every time the adjustment patch CP is picked up, and a lot of image data of the reference chart KC exists.

  Therefore, in the image forming apparatus 1 of the present embodiment, the colorimetry control unit 120 averages the RGB values of each patch of the reference chart KC captured by the imaging unit 100 for each predetermined imaging region, for example, for each color of the patch. The average value is temporarily stored in the non-volatile memory 125 as the colorimetric reference RGB value RdsGdsBds.

  In this case, the colorimetric control unit 120 is limited to the average value of the RGB values imaged a plurality of times among the RGB values of each patch of the reference chart KC imaged a plurality of times by the imaging unit 100 together with the colorimetry adjustment sheet CS. Instead, for example, an appropriate RGB value such as the RGB value captured first, the RGB value captured at an appropriate number of times, and the median RGB value may be set as the colorimetric reference RGB value RdsGdsBds.

  The colorimetric control unit 120 uses the third linear transformation matrix (to be described later) to convert the colorimetric RGB values stored in the frame memory 121 to the colorimetric value calculation unit 126 of the calculation unit 124 to initialize the colorimetric RGB data. Conversion to the value RsGsBs (steps S22 and S23).

  The calculation unit 124 of the color measurement control unit 120 uses the converted initialization color measurement target RGB value RsGsBs as the color measurement target RGB value of the first embodiment (step S24), and performs the color measurement processing performed in the first embodiment. This is executed to obtain the Lab colorimetric value (step S25).

  In the image forming apparatus 1 according to the present exemplary embodiment, the colorimetric value calculation unit 126 of the calculation unit 124 determines the third linear conversion matrix as illustrated in FIGS. 33 and 34.

  That is, as shown in FIG. 33, the colorimetric value calculation unit 126 of the calculation unit 124 also captures the patch of the reference chart KC when the imaging unit 100 captures the reference color patch KP of the reference sheet KS at the initial stage. When the initial reference RGB value RdGdBd stored in the nonvolatile memory 125 and the color measurement adjustment color patch CP of the color measurement adjustment sheet CS are imaged by the imaging unit 100 during color measurement, the patch of the reference chart KC is imaged. The colorimetric reference RGB value RdsGdsBds stored in the nonvolatile memory 125 is read from the nonvolatile memory 125, and a third linear conversion matrix for converting the colorimetric reference RGB value RdsGdsBds to the initial reference RGB value RdGdBd is obtained. The obtained third linear transformation matrix is stored in the nonvolatile memory 125.

  That is, in FIG. 34, the points indicated by white dots in FIG. 34 (a) are points where the initial reference RGB value RdGdBd is plotted in the rgb space, and the filled points are the colorimetric reference RGB values RdsGdsBds as rgb. This is a point plotted in space. As can be seen from FIG. 34 (a), the value of the colorimetric reference RGB value RdsGdsBds varies from the value of the initial reference RGB value RdGdBd, and the direction of variation in the rgb space is shown in FIG. 34 (b). As indicated by the arrows, the directions are generally the same, but the direction of deviation differs depending on the hue. As described above, the reason why the RGB values fluctuate even when the patches of the same reference chart KC are imaged includes a change with time of the illumination light source 107 and a change with time of the two-dimensional image sensor 105.

  As described above, the RGB values of the color measurement target when the color measurement adjustment patch CP of the color measurement adjustment sheet CS is imaged in the state that is fluctuated when the patches of the same reference chart KC are imaged are the same as those in the first embodiment. When the colorimetric value is obtained in this way, the colorimetric value is affected by the variation.

  In view of this, the image forming apparatus 1 according to the present exemplary embodiment uses the estimation method such as the least square method between the initial reference RGB value RdGdBd and the colorimetric reference RGB value RdsGdsBds to initially set the colorimetric reference RGB value RdsGdsBds. A third linear conversion matrix to be converted into the reference RGB value RdGdBd is obtained, and the colorimetric adjustment color patch CP of the colorimetry adjustment sheet CS is imaged by the imaging unit 100 using the third linear conversion matrix, and the nonvolatile memory 125 is obtained. The colorimetric object RGB values stored in the first colorimetric object RGB value RsGsBs are converted to the first colorimetric object RGB value RsGsBs of the first embodiment as the colorimetric object RGB value of the first embodiment. The colorimetric processing performed in the embodiment is executed to acquire the Lab colorimetric value.

  This third linear transformation matrix may be not only the first-order but also a higher-order nonlinear matrix. If the nonlinearity is high between the rgb space and the XYZ space, the third-order linear transformation matrix is set as a higher-order matrix. Conversion accuracy can be improved.

  The imaging unit 100 has been described with respect to the case where the optical path length changing member 108 is disposed in the optical path between the recording medium P and the two-dimensional image sensor 105 through the opening 102c. 108 is not limited to the case where it is disposed in the optical path. For example, as shown in FIGS. 35 and 36, in addition to the optical path length changing member 108, an optical path length changing member 109 is provided in the opening 102b. You may arrange | position in the optical path of the reference | standard sheet | seat KS and the two-dimensional image sensor which are arrange | positioned.

  In this case, the optical path length changing member 109 has a length Lq shorter than the length Lp of the optical path length changing member 108, and the lift amount C is calculated from the above formula (1). The focal length L calculated from (2) is set to be the same as the focal length L of the light passing through the optical path length changing member 108.

  Accordingly, when the optical path length changing members 108 and 109 are arranged on both the recording medium P side and the reference chart KC in this way, the focal length L to the recording medium P and the focal distance L to the reference chart KC are the same. And more accurate colorimetry can be performed.

  In the imaging unit 100, the optical path length changing member 108 or the optical path length changing members 108 and 109 are disposed on one side of the recording medium P or on both the recording medium P side and the reference chart KC side. As shown in FIG. 37, data necessary for the colorimetric processing can be acquired without providing an optical path length changing member on either the recording medium P side or the reference chart KC side. In this case, there is a difference in the optical path length between the reference chart KC and the recording medium P, but if it is within the focal depth of the lens 106, the colorimetric processing can be imaged without any problem.

  Also in this embodiment, the CPU 51 checks whether or not there is a defect in each nozzle of the recording heads 20y to 20k by the nozzle state detection unit 40 at least at any timing before and after the color adjustment process. Nozzle state detection processing is performed. Then, the CPU 51 performs a nozzle state detection process, and any of the nozzles of the recording heads 20y to 20k from the driving nozzles of the recording heads 20y to 20k and the detection signal So via the recording head driver 56 is defective. The detected nozzle missing information is stored in the nonvolatile memory 54.

  Then, the CPU 51 passes the nozzle defect information detected and stored in the nonvolatile memory 54 to the colorimetry control unit 120.

  In the color measurement control unit 120, the color measurement value calculation unit 126 of the calculation unit 124 stores the nozzle defect information received from the CPU 51 in the nonvolatile memory 125 and uses it for data processing in the color adjustment processing.

  In other words, the colorimetric value calculation unit 126 reads nozzle missing information from the nonvolatile memory 125 during color adjustment processing, excludes it from the target of the colorimetric target RGB value based on the colorimetric adjustment color patch CP, and sets the colorimetric value. Get the.

  In the image forming apparatus 1 of the present embodiment, when there is a nozzle defect as shown in FIG. 15 of the first embodiment, the CPU 51 determines the position of the defective nozzle in this case in the colorimetric adjustment color that is known in advance. It is easily specified from the relationship between the patch CP and the nozzle numbers (NO) of the recording heads 20y to 20k.

  Further, when the nozzle state detection process is executed based on the imaging data of the imaging unit 100, the CPU 51 determines the imaging range of the imaging unit 100 and the colorimetric adjustment color from the positional relationship between the recording heads 20y to 20k and the imaging unit 100. The relationship of the patch CP is determined, and the position of the defective nozzle is specified.

  Therefore, for example, in the case of FIG. 15, the CPU 51 can easily determine the exclusion start line (M) to be excluded from the color measurement target.

  Note that the number of excluded lines (ΔM) varies depending on the size of the ink droplet attached to the recording medium P and the imaging optical system of the imaging unit 100. For example, as shown in FIG. 38, when the ink droplet size attached to the recording medium P is 100 μm, and the imaging optical system of the imaging unit 100 has a pixel size of 2 μm and a magnification of 10 times, the excluded region ΔM ΔM = 100 / (2 × 10) = 5 lines. Actually, since it shifts up and down, it is necessary to make the exclusion region 6 lines or more. In addition, depending on the recording medium P, the degree of ink bleeding differs and the ink droplet size changes. Therefore, the size of the excluded area (number of excluded lines) is appropriately set according to the recording medium P.

  Also in the image forming apparatus 1 of the present embodiment, when there is a large amount of exclusion data, as described in the first embodiment, the data amount corresponding to the missing nozzle may be supplemented.

  In this way, colorimetric accuracy can be improved.

  Further, in each of the embodiments described above, the color measurement process is performed by the CPU 51 or the color measurement control unit 120 of the image forming apparatus 1. However, the color measurement process need not be executed inside the image forming apparatus 1, for example, 39, as an image forming system (color measurement system) 200, an image forming apparatus 210 is connected to an external apparatus 220, and image data captured by the image forming apparatus 210 is stored in the external apparatus 220. The external device 220 performs color adjustment processing that includes colorimetric processing, and outputs the image data after color adjustment to the image forming device 210. The image forming device 210 converts the image data from the external device 220 into image data. An image may be formed based on this.

  That is, the image forming apparatus 210 includes an engine 211, an operation display unit 212, an I / F unit 213, other I / F units 214, and the like, and each unit is connected by a bus 215.

  In addition, the external device 220 can use, for example, a computer having a normal hardware configuration and software configuration, and includes a color adjustment program including a color measurement program that executes a color adjustment process accompanying the color measurement process of the present invention as software. The color adjustment process accompanied by the colorimetric process is executed by introducing. The external device 220 includes a CPU 221, a memory unit 222, an image processing unit 223, a communication I / F unit 224, an I / F unit 225, and the like, and each unit is connected by a bus 226. The memory unit 222 includes a ROM 227, a RAM 228, a hard disk (HDD) 229, and the like.

  The image forming apparatus 210 is connected to the external apparatus 220 via a line 230 by an I / F unit 213. The line 230 is a dedicated line, a network such as a LAN (Local Area Network), the Internet, and the like, and is wired. Or wireless.

  The image forming apparatus 210 forms and outputs an image on a recording medium by the engine 211 based on the image data sent from the external apparatus 220 under the control of the external apparatus 220. The engine 211 forms an image on a recording medium by an ink ejection method or the like, and the operation display unit 212 includes various operation keys and a display such as an LCD (Liquid Crystal Display). Various necessary operations are performed using the operation keys, and various information notified from the image forming apparatus 210 to the user is displayed on the display. The other I / F unit 214 is used for connecting an expansion unit.

  The engine 211 includes a carriage 6 that moves in the main scanning direction similar to that described in the above-described embodiment, and the imaging unit 30 illustrated in the first embodiment or the imaging illustrated in the second embodiment is disposed on the carriage 6. Part 100 is attached. The image forming apparatus 210 forms the color measurement adjustment patch CP on the recording medium based on the color patch data of the color measurement adjustment color patch CP sent from the external apparatus 220 under the control of the CPU 221 of the external apparatus 220. Then, the color measurement adjustment sheet CS is generated, and the color measurement adjustment patch CP of the generated color measurement adjustment sheet CS is read by the imaging unit and transmitted to the external device 220 via the I / F unit 213.

  The external device 220 stores in the hard disk 229 or the ROM 227 an image formation control program for controlling the operation of the image forming apparatus 210, a color adjustment program for performing color adjustment processing accompanying colorimetric processing of the present invention, and necessary data. The CPU 221 controls the image forming apparatus 210 based on a program in the ROM 227 or the hard disk 229, thereby executing basic processing as the image forming apparatus 210 and executing color adjustment processing accompanying colorimetric processing of the present invention.

  The hard disk 229 stores the program and various data necessary for executing the color adjustment process and the nozzle state detection process, in particular, a plurality of reference colors arranged in the reference sheet KS described in the above embodiment. At least one of the Lab and XYZ values of the color measurement result of the patch KP (both the Lab value and the XYZ value in FIG. 11), the reference patch KP of the reference sheet KS is read by the imaging unit of the image forming apparatus 210. Imaging reference RGB values, first linear transformation matrix, neighborhood point table and second linear transformation matrix, and reference chart read together with the reference sheet KS when the imaging unit is the imaging unit 100 of the second embodiment The initial reference RGB value RdGdBd of each color patch of KC and the color measurement adjustment color patch CP of the color measurement adjustment sheet CS were read. Third linear transformation matrix for converting the color measurement at the reference RGB values RdsGdsBds and colorimetry at reference RGB values RdsGdsBds the reference patch of the reference chart KC read to come to an initial reference RGB value RdGdBd is stored.

  The communication I / F unit 224 is connected to an image processing apparatus such as a scanner apparatus, a composite apparatus, or another external apparatus via a line such as a network, and receives image data that causes the image forming apparatus 210 to output an image.

  The image processing unit 223 performs various image processes necessary for forming and outputting the image data with the engine 211 of the image forming apparatus 210.

  As described above, the CPU 221 controls the operation of the image forming apparatus 210, and the CPU 51 of the first embodiment or the calculation unit 124 of the color measurement control unit 120 of the second example, in particular, the color measurement value calculation unit 126. The colorimetric processing and nozzle state detection processing to be executed are executed to obtain a colorimetric value, color adjustment is performed on the image data based on the colorimetric value, and the result is output to the image forming apparatus 210.

  In the image forming system 200 in FIG. 39, the operation of the image forming apparatus 210 is controlled by the external apparatus 220. However, the image forming apparatus 210 itself includes a controller such as a CPU. The external device 220 may execute only the color measurement process for which the controller controls and obtains the color measurement value, or only the color adjustment process including the color measurement process.

  As described above, when color adjustment processing including color measurement processing or color measurement processing is executed at least by an external device of the image forming apparatus 210, the color reproducibility can be appropriately improved at low cost even in the inexpensive image forming apparatus 210. it can.

  In the above description, the color adjustment process is performed by the image forming apparatus 1 or the external apparatus 220. However, whether or not the color adjustment process is performed is an arbitrary action by the user, and is not necessarily limited to the image forming apparatus 1 or the external apparatus 220. There is no need to perform color adjustment processing. By measuring the colors actually output by the image forming apparatus, the user can know the colorimetric values in the L * a * b * color space or the like. The act using the colorimetric values is arbitrary. For example, the color of the image before the user inputs it to the image forming apparatus or the image forming system may be changed. In addition, even when the output color of the image forming apparatus is deviated from the input color, it is also possible to output using the shifted color. Thus, the color adjustment process is a user's arbitrary action.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to that described in the above embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Main body case 3 Main body frame 4 Main guide rod 5 Sub guide rod 6 Carriage 6a Connection piece 7 Timing belt 8 Drive pulley 9 Drive pulley 10 Main scanning motor 11 Cartridge part 12 Maintenance mechanism part 12a Waste liquid tank 13 Cover 14 Platen 15 Encoder sheet 20 Recording head 20y, 20m, 20c, 20k Recording head 21 Encoder sensor 30 Imaging unit 31 Printed circuit board 32 Light source 33 Light receiving element unit 34 Two-dimensional image sensor 35 Lens 40 Nozzle state detection unit 41 Light emitting unit 41a Light emitting element 41b Collimating lens 41c Aperture 42 Light receiving part 51 CPU
52 ROM
53 RAM
54 Nonvolatile Memory Tb1 Memory Table 55 Main Scan Driver 56 Recording Head Driver 57 Paper Transport Unit 58 Sub Scan Driver 60 Camera Controller 61 Sub CPU
62 Data storage memory 63 SRAM
64 PWM controller 65 I2C controller 66 Host CPU I / F
67 VIDEO I / F
68 Selection / averaging section 69 Bus P Recording medium PG Patch image BS Spectrometer KS Reference sheet CS Color measurement adjustment sheet CP Color measurement adjustment color patch 100 Imaging section 101 Substrate 102 Frame body 102a Lower surface section 102b Opening section 102c Opening section 102d Recessed portion 102e Holding plate 103 Fastening member 104 Image sensor unit 105 Two-dimensional image sensor 106 Lens 107 Illumination light source 108, 109 Optical path length changing member 110 Image processing unit 111 Interface unit 112 A / D conversion unit 113 Shading correction unit 114 White balance correction unit 115 γ correction unit 116 image format conversion unit 120 color measurement control unit 121 frame memory 122 timing signal generation unit 123 light source drive control unit 124 calculation unit 125 nonvolatile memory 126 color measurement value calculation unit 2 0 image forming system 210 the image forming apparatus 211 engine 212 operation display unit 213 I / F unit 214 other I / F section 215 bus 220 external device 221 CPU
222 Memory unit 223 Image processing unit 224 Communication I / F unit 225 I / F unit 226 Bus 227 ROM
228 RAM
229 Hard disk 230 Line d Gap Lo Center line KC Reference chart Pa to Pd Reference color patch row Pe Dot diameter measurement pattern row lk Distance measurement line mk Chart position specifying marker

JP 2012-063270 A

Claims (8)

Image forming means for forming an image of a plurality of colors on a recording medium;
Image defect detection means for detecting a defect state of an image formed by the image forming means;
Imaging means for imaging a colorimetric object formed on the recording medium by the image forming means over a predetermined imaging range;
Colorimetry that performs colorimetry based on the imaging result of the effective imaging range by the imaging unit, with the range excluding the missing range detected by the image loss detection unit as the effective imaging range among the imaging range by the imaging unit Means,
An image forming apparatus comprising: The image forming unit includes:
Having a plurality of nozzles, ejecting ink droplets from the nozzles to form the image,
The image defect detection means includes
Light emitting means for emitting detection light toward the ink droplets ejected from each nozzle;
A light receiving means for receiving the scattered light of the detection light by the ink droplets and outputting a detection signal according to the amount of light received;
A defect determining means for determining a defect state of an image based on a detection signal output from the light receiving means;
The image forming apparatus according to claim 1, further comprising: The image defect detection means includes
Pattern image formation control means for causing the image forming means to form a predetermined image defect detection pattern image on the recording medium;
A defect image determining unit that causes the image defect detection image to be captured by the image capturing unit and determines a defect state of the image based on pattern image data output from the image capturing unit;
The image forming apparatus according to claim 1, further comprising: The missing image determination means includes
The pattern image data output from the image pickup means is compared with expected pattern image data obtained when the image pickup means picks up the image defect detection pattern image that does not have a defect in advance. The image forming apparatus according to claim 3, wherein the determination is made. The image defect detection means includes
Pattern image data output from the imaging unit by causing the imaging unit to image the subject of the color measurement target formed by the image forming unit as the image defect detection pattern image at the color measurement timing by the color measuring unit. 5. The image forming apparatus according to claim 3, wherein a defect state of the image is detected on the basis of the image quality. The colorimetric means is
The image according to any one of claims 1 to 5, wherein the color measurement is performed by complementing the missing range excluded from the imaging range by the imaging means with data of the effective imaging range. Forming equipment. An image defect detection processing step for detecting a defect state of the image formed by an image forming unit that forms an image of a plurality of colors on a recording medium;
An imaging process step of imaging a subject to be colorimetrically formed on the recording medium by the image forming unit over a predetermined imaging range;
Based on the imaging result of the effective imaging range in the imaging processing step, the effective imaging range is defined as the effective imaging range of the imaging range in the imaging processing step, excluding the defective range detected in the image defect detection processing step. A colorimetric processing step for performing colorimetry;
A colorimetric method characterized by comprising: To the control processor,
An image defect detection process for detecting a defect state of the image formed by an image forming unit that forms an image of a plurality of colors on a recording medium;
An imaging process for imaging a colorimetric object formed on the recording medium by the image forming unit over a predetermined imaging range;
Of the imaging range in the imaging process, a range excluding the defective range detected in the image defect detection process is set as an effective imaging range, and colorimetry is performed based on the imaging result in the imaging process of the effective imaging range. Color measurement processing to be performed,
A colorimetric program characterized by causing