JP2005319676A - Image forming apparatus and method of controlling it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that can readily represent correction of a characteristic of an output of a sensor, density gradation at an arbitrary time point and controlling of a color balance. <P>SOLUTION: This image forming apparatus comprises a detection means for detecting a density or a chroma of an image formed on a recording medium and an image forming means for controlling the forming of an image by using the detection information acquired by the detection means. The detection information is recorded on the recording medium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus represented by a printer, a copying machine, and the like, and a control method thereof, and more particularly to a technique for improving image quality in the image forming apparatus.

  In recent years, color image forming apparatuses employing an electrophotographic system, an ink jet system, or the like typified by a printer or a copying machine have been required to improve the output image quality.

  However, in the color image forming apparatus, when there is a change in each part of the apparatus due to a change in environment or a long time use, the density and color of the obtained image change.

  In particular, in the case of an electrophotographic color image forming apparatus, even a slight environmental change may cause a color change and there is a risk of losing the color balance. have. For example, for each color toner, it has gradation correction means such as several kinds of exposure amount and development bias according to absolute humidity, a look-up table (LUT) for converting image data, etc. Based on the measured absolute humidity, process conditions at that time and optimum values for gradation correction are selected. In addition, a density detection toner patch is formed on the intermediate transfer member, the photosensitive member, etc. with a single color toner so that a constant color and gradation of the color can be obtained even if variations in each part of the apparatus occur. The density of an unfixed single color toner patch is detected by a density detection sensor for unfixed toner (hereinafter referred to as a density sensor), and the detection result is fed back to process conditions such as exposure amount and development bias, and to gradation correction means such as LUT. By performing the density control over the above, it is configured to obtain stable color and color gradation (see, for example, Patent Documents 1 and 2).

  However, density control using the above density sensor is to detect patches by forming patches on an intermediate transfer member, drum, etc., and to control changes in image color balance due to subsequent transfer to a recording medium and fixing. Not done. The color balance also changes depending on the transfer efficiency in transferring the toner image to the recording medium, and heating and pressurization by fixing. This change cannot be handled by density control using the density sensor.

  Therefore, cyan (C), magenta (M), yellow (Y), and black (K) single-color gradation patches or C, M, and Y mixed-color patches are formed on the recording medium, and are fixed on the recording medium after fixing. A color image forming apparatus provided with a sensor (hereinafter referred to as a color sensor) for detecting the density or chromaticity of the patch is also proposed (see, for example, Patent Document 3).

  In this color image forming apparatus, the final output image formed on the recording medium is fed back to the calibration table for correcting the exposure amount of the image forming unit, the process conditions, and the density-gradation characteristics. Density or chromaticity can be controlled. This color sensor uses, for example, three or more light sources having different emission spectra such as red (R), green (G), and blue (B) as light emitting elements, or the light emitting element emits white light (W). And three or more types of filters having different spectral transmittances such as red (R), green (G), and blue (B) are formed on the light receiving element. As a result, three or more different outputs such as RGB output can be obtained.

Even in an ink-jet color image forming apparatus, the color balance changes due to a change in the ink discharge amount with time, an environmental difference, and an individual difference of the ink cartridge, and the density-gradation characteristics cannot be kept constant. Therefore, there is a color image forming apparatus in which the ink head is replaced with a color sensor, and the density or chromaticity of the patch on the recording medium is detected and the density or chromaticity is controlled.
Japanese Patent Application Laid-Open No. 7-055703 Japanese Patent No. 3430702 JP 2003-084532 A

  However, in this method, changes in sensor characteristics and differences among individuals are problematic.

  Changes and differences in sensor characteristics include variations in the spectral characteristics of the light-emitting and light-receiving elements that make up the sensor, changes over time in the light-emitting and light-receiving parts, changes in ambient temperature, and many transfer materials pass near the sensor during normal printing. As a result, paper dust, toner or ink scatters, and this is caused by a decrease in sensor output due to accumulation or adhesion on the sensor surface. If there are changes or differences in the characteristics of the sensor, density gradation and color balance control may not be performed correctly, and may worsen.

  In the present invention, by correcting the characteristics of the sensor itself, density gradation and color reproducibility are stabilized, and density gradation and color stability among a plurality of apparatuses are improved.

  To correct the sensor characteristics, there is a method that uses a white reference plate, which is often used as a reference for calibrating the sensor output. Or there is a possibility that the ink adheres and cannot be used as a reference plate. Further, in the case of only white, since the number of reference objects is small, the calibration accuracy is not sufficient.

  The present invention is capable of correcting a sensor in an image forming apparatus, and recording detection information on a transfer material so that a user can easily maintain, restore, or restore density gradation and color balance control at an arbitrary time. The purpose is to provide superior technology in that it can be shared between the two.

  In order to solve the above-described problems and achieve the object, an image forming apparatus of the present invention includes a detection unit that detects the density or chromaticity of an image formed on a recording medium, and detection information obtained by the detection unit. And image forming means for controlling the formation of an image using the image sensor, and the detection information is recorded on a recording medium.

  In addition, the image forming apparatus of the present invention includes a detection unit that detects the density or chromaticity of an image formed on a recording medium, detection information obtained by the detection unit, and detection information of the same image detected in the past. And a correcting means for correcting the characteristics of the detecting means using the comparison result.

  Also, the control method of the image forming apparatus of the present invention controls the image formation using the detection means for detecting the density or chromaticity of the image formed on the recording medium and the detection information obtained by the detection means. An image forming apparatus control method comprising: an image forming unit; and a step of recording the detection information on a recording medium.

  According to another aspect of the present invention, there is provided a control method for an image forming apparatus including a detection unit that detects density or chromaticity of an image formed on a recording medium, the detection method obtained by the detection unit. A comparison step of comparing information with detection information of the same image detected in the past, and a correction step of correcting the characteristics of the detection means using the comparison result.

  The present invention can also be applied to a program for causing a computer of the image forming apparatus to execute the control method, a recording medium for storing the program, and the like.

  With the above configuration, the user can easily reproduce density gradation and color balance control at the time of detection in the past by storing images detected in the past on the recording medium and corresponding detection information. It becomes possible.

  As described above, according to the present invention, by recording the detection information on the recording medium, the user can reproduce the sensor output characteristic correction, density gradation and color balance control at an arbitrary time point. Easy to do.

  Further, changes in sensor output characteristics and individual differences can be corrected using images used for detection in the past and detection information at that time without using a sensor output calibration reference or the like.

  Further, density gradation and color stability can be further improved by correcting the sensor output characteristics.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  The embodiment described below is an example as means for realizing the present invention, and should be appropriately modified or changed according to the configuration and various conditions of the apparatus to which the present invention is applied. It is not limited to the embodiment.

Further, the present invention supplies a storage medium (or recording medium) storing software program codes for realizing the functions of a color image forming apparatus according to an embodiment described later to the system or apparatus, and the computer of the system or apparatus Needless to say, this can also be achieved by (or CPU or MPU) reading and executing the program code stored in the storage medium.
[First Embodiment]
FIG. 1 is a block diagram showing a tandem color image forming apparatus that employs an intermediate transfer member 27 as an example of an electrophotographic color image forming apparatus.

  First, the operation of the electrophotographic color image forming apparatus will be described with reference to FIG.

  As shown in FIG. 1, in the color image forming apparatus, an electrostatic latent image is formed in an image forming unit by exposure light controlled by an image processing unit 43 (to be described later in FIG. 2) based on an image signal. The image is developed to form a single-color toner image, the single-color toner images are superimposed to form a multi-color toner image, and the multi-color toner image is transferred to a transfer material (recording medium) 11 such as paper. The multi-color toner image on the material 11 is fixed. The image forming unit is a sheet feeding unit 21 and photosensitive members (hereinafter referred to as photosensitive drums) 22Y, 22M, 22C, 22K for each station arranged in parallel for the development colors. Injection chargers 23Y, 23M, 23C, and 23K constituting injection charging means as primary charging means, toner cartridges 25Y, 25M, 25C, and 25K, developing devices 26Y, 26M, 26C, and 26K constituting developing means, medium It is constituted by the transfer member 27, the transfer roller 28 and the fixing unit 30.

  The photosensitive drums 22Y, 22M, 22C, and 22K are configured by applying an organic optical transmission layer on the outer periphery of an aluminum cylinder, and are rotated by a driving force of a driving motor (not shown). The driving motor is a photosensitive drum 22Y. , 22M, 22C, and 22K are rotated counterclockwise in accordance with the image forming operation.

  As primary charging means, four injection chargers 23Y, 23M, 23C, and 23K for charging the photosensitive drums of yellow (Y), magenta (M), cyan (C), and black (K) are provided for each station. In configuration, each injection charger is provided with a sleeve 23YS, 23MS, 23CS, 23KS.

  Exposure light to the photosensitive drums 22Y, 22M, 22C, and 22K is sent from the scanner units 24Y, 24M, 24C, and 24K, and the electrostatic latent images are selectively exposed by exposing the surfaces of the photosensitive drums 22Y, 22M, 22C, and 22K. An image is formed.

  As developing means, in order to visualize the electrostatic latent image, four developing units 26Y, 26M for developing yellow (Y), magenta (M), cyan (C), and black (K) for each station, Each developing device is provided with a sleeve 26YS, 26MS, 26CS, and 26KS. Each developing device is detachably attached.

  The intermediate transfer member 27 is in contact with the photosensitive drums 22Y, 22M, 22C, and 22K, and rotates clockwise when forming a color image. The toner image is transferred.

  Thereafter, a transfer roller 28 described later comes into contact with the intermediate transfer member 27 and conveys the transfer material 11 while sandwiching the transfer material 11, and the multicolor toner image on the intermediate transfer member 27 is transferred to the transfer material 11.

  The transfer roller 28 contacts the transfer material 11 at the position 28a while the multicolor toner image is transferred onto the transfer material 11, and is separated to the position 28b after the printing process.

  The fixing unit 30 melts and fixes the transferred multi-color toner image while conveying the transfer material 11, and as shown in FIG. 1, the fixing roller 31 for heating the transfer material 11 and the transfer material 11 are fixed to the fixing roller. A pressure roller 32 is provided for pressure contact with 31.

  The fixing roller 31 and the pressure roller 32 are formed in a hollow shape, and heaters 33 and 34 are incorporated therein, respectively.

  That is, the transfer material 11 holding the multicolor toner image is conveyed by the fixing roller 31 and the pressure roller 32, and heat and pressure are applied to fix the toner on the surface.

  After the toner image is fixed, the transfer material 11 is discharged to a discharge tray (not shown) by a discharge roller (not shown) and the image forming operation is finished.

  The cleaning unit 29 cleans the toner remaining on the intermediate transfer member 27. The waste toner after the four-color multicolor toner image formed on the intermediate transfer member 27 is transferred to the transfer material 11 is: It is stored in a cleaner container (not shown).

  FIG. 2 is a flowchart illustrating an example of processing in the image processing unit 43 of the image forming apparatus.

  In step S121, a device RGB signal (hereinafter referred to as DevRGB) in which the RGB signal representing the color of the image sent from the personal computer 45 is matched with the color gamut of the image forming apparatus using the color matching table 431 prepared in advance. ).

  In step S122, the DevRGB signal is converted into a CMYK signal, which is a toner color material color of the image forming apparatus, using a color separation table 432 prepared in advance.

  In step S123, C'M'Y'K 'obtained by correcting the CMYK signal by correcting the density-gradation characteristics using the calibration lookup table 433 for correcting the density-gradation characteristics specific to each image forming apparatus. Convert to signal.

  In step S124, halftone processing 434 such as dithering is performed.

  In FIG. 1, an unfixed toner density detection sensor 41 is disposed toward the intermediate transfer body 27 and measures the density of a toner patch formed on the surface of the intermediate transfer body 27.

  An example of the configuration of the unfixed toner density detection sensor 41 is shown in FIGS.

  A light emitting element 51 such as an infrared LED, a light receiving element 52 such as a photodiode or Cds, an optical element 53 used for coupling the light receiving / emitting element, an IC (not shown) for processing the received light data, and the like (not shown) that accommodates these Consists of holders.

  4A shows a configuration in which the sum of the regular reflection component and the irregular reflection component is detected, and FIG. 4B shows a configuration in which only the irregular reflection component is detected without being affected by the specular reflection. What is necessary is just to use suitably according to an optical reflection characteristic. The density correction is performed by feeding back the detection result to the calibration lookup table 433.

  Next, a correction method using a color sensor will be described.

  In the image forming apparatus shown in FIG. 1, a color sensor 42 serving as a chromaticity detecting unit is disposed on the downstream side of the fixing unit 30 in the transfer material conveyance path toward the image forming surface of the transfer material 11, and is transferred by the image forming unit. The density or chromaticity control is performed by detecting the density of the single color patch or the chromaticity of the mixed color patch formed on the material 11 and correcting the calibration lookup table 433 of the image processing unit 43 based on the detection result. Do. The color sensor can measure the actual density on the transfer material and can measure the chromaticity of a mixed color of two or more colors with respect to the above-described density detection sensor for unfixed toner, so that correction with higher accuracy is possible.

  The configuration of the color sensor 42 is shown in FIG.

  The difference from the unfixed toner density detection sensor 41 is that a light source that emits white (W) is used for the light emitting element 54 to detect chromaticity, and red (R), green ( Three types of filters 55 having different spectral transmittances of G) and blue (B) are prepared. There is also a method of using light sources having different emission spectra for independently emitting red (R), green (G), and blue (B) without using a filter.

  FIG. 5 shows an example of a density-gradation characteristic control patch pattern after fixing formed on the transfer material 11. The patch pattern for density-gradation characteristic control is a gray gradation patch pattern which is the center of the color reproduction range and is a very important color for adjusting the color balance. It is composed of a gray gradation patch 64 by black (K) and a process gray gradation patch 65 in which cyan (C), magenta (M), and yellow (Y) are mixed, and 64a and 65a, 64b and 65b, and so on. As described above, in the standard color image forming apparatus, the gray gradation patch 64 and the CMY process gray gradation patch 65 with K having close chromaticity are arranged side by side in pairs. The RGB output value of this patch is detected by the color sensor 42.

  FIG. 3 is a flowchart showing correction processing by the color sensor.

  In step S131, a patch pattern 60 is created based on a calibration lookup table 433 prepared in advance.

  In step S <b> 132, the RGB output value of the patch pattern 60 after fixing on the transfer material 11 is detected by the color sensor 42.

  In step S133, RGB output values that are device-specific output values are converted into Lab data that is a standard color space.

  In step S134, based on the difference in Lab data between the gray gradation patch 64 of black (K) and the process gray gradation patch 65 in which cyan (C), magenta (M), and yellow (Y) are mixed, K = The calibration lookup table 433 is corrected so as to be CMY.

  As described above, since the density-gradation characteristics change due to environmental changes and long-time use, it is very effective to perform the above correction at a predetermined timing. Here, a correction method using a gray tone patch that enables highly accurate correction has been described. However, the chromaticity of a mixed color obtained by mixing two colors or three colors of yellow, magenta, and cyan other than gray is measured. Even correction is possible.

  In addition to the calibration lookup table 433, the color matching table 431 and the color separation table 432 can be modified.

  FIGS. 6A and 6B are flowcharts showing a method for correcting color sensor characteristics using detection information detected in the past in the present embodiment, and FIG. 7 shows a color sensor according to the first embodiment. It is a figure which shows an example of the patch pattern in the correction method of, and detection information.

  A color sensor correction method according to this embodiment will be described with reference to FIGS. 1, 3, 5 to 7, and 12.

  First, the transfer material 11 on which the patch pattern 60 created for density or chromaticity control as shown in FIG. 5 is formed is conveyed to the position of the color sensor 42.

  Next, in step S <b> 111 in the flowchart of FIG. 6A, the color sensor 42 detects the RGB output value of the patch pattern 60.

  In step S112, the user refeeds the transfer material 11 discharged after the detection to the paper feed tray.

  In step S113, the RGB output value of the patch pattern 60 detected by the color sensor 42 in step S111 is printed on the transfer material 11 in a portion other than the image as a numerical value 61 as illustrated in FIG.

  Up to step S113, the recording of the detection information on the transfer material 11 and the storage of the RGB output values of the patch pattern 60 in step S111 are completed.

  Next, using the transfer material on which the image to be detected has already been printed and the detection information is recorded, a plurality of sheets are printed with the same image forming apparatus to correct the sensor characteristics that have changed over time, or to form a different image. A method for correcting the sensor characteristics in the apparatus will be described with reference to the flowchart of FIG.

  In response to a request from the color image forming apparatus or the user, in step S114, an operation for correcting the output characteristics of the color sensor 42 at the time of step S111 is started.

  In step S115, the color sensor 42 detects the RGB output value of the patch pattern 60 on the transfer material 11. Here, the patch pattern 60 on the transfer material 11 means that the RGB output value has been detected in the past, and the detection information is recorded on the transfer material 11.

  In step S116, the user inputs the numerical value 61 recorded in step S113 from the operation panel 44 of the color image forming apparatus.

  In step S117, the color sensor control unit 435 in the image processing unit 43 compares the numerical value 61 read in step S116 with the RGB output value detected in step S115.

  In step S118, the color sensor control unit 435 obtains the difference in output characteristics compared in step S117, creates a color sensor output correction table from the difference, and corrects the output characteristics of the color sensor 42.

  This output characteristic correction method will be described with reference to FIG. The horizontal and vertical axes of the graph represent the input and output of the color sensor, respectively.

  The RGB output characteristics at the time of creating detection information read in step S116 are as shown in FIG. 12A. An output b1 is obtained for the input a1 and an output b2 is obtained for the input a2. The RGB output characteristics newly detected in step S115 are shown in FIG. 12B, and output b1 ′ is obtained for input a1 and b2 ′ is obtained for input a2.

  In step S118, the color sensor control unit 435 in the image processing unit 43 displays a one-dot chain line graph symmetrical to the newly detected RGB output characteristics with respect to the RGB output characteristics at the time of detection information creation. A color sensor output correction table as shown in the figure is created, and these are multiplied so that an output b1 with respect to the input a1 and an output b2 with respect to the input a2. As a result, the same RGB output characteristics as when the detection information was created can be obtained.

  Although an example using two control points a1 and a2 has been described above, correction may be performed using three or more control points. In this case, data between control points may be linearly interpolated or spline interpolated.

According to the color sensor correction method described above, by using a relative comparison with past detection information without using a sensor output characteristic correction reference, the effects of sensor contamination due to scattering of paper dust, toner, or ink, Variations in spectral characteristics and changes with time can be corrected, and color balance control required by the user can be reproduced.
[Second Embodiment]
FIGS. 8A and 8B are flowcharts illustrating a method for correcting color sensor characteristics using detection information obtained in the past in the present embodiment, and FIG. 9 illustrates the second embodiment. It is a figure which shows an example of the patch pattern and detection information in the correction method of a color sensor.

  The image forming apparatus according to the second embodiment includes a reading unit that reads an automatic recognition symbol such as a barcode, and the detection information is recorded by the automatic recognition symbol and does not require input by the user. It can be read.

  A color sensor correction method according to the second embodiment will be described with reference to FIGS. 1, 8, and 9.

  First, a method for recording detection information with automatic recognition symbols will be described with reference to the flowchart of FIG.

  In step S <b> 211, the color sensor 42 detects the RGB output value of the patch pattern 60.

  In step S212, the user re-feeds the transfer material 11 discharged after detection to the paper feed tray.

  In step S213, a process of converting the RGB output value obtained in step S211 into the automatic recognition symbol 62 is performed.

  In step S214, the automatic recognition symbol 62 is printed on the transfer material 11 in a portion other than the image. Here, the symbolized information may be anything as long as it can be read by a reading unit included in the image forming apparatus, such as a barcode.

  Up to step S214, the recording of the detection information onto the transfer material 11 and the storage of the RGB output values of the patch pattern 60 in step S211 are completed.

  Next, using a transfer material on which an image to be detected has already been printed and on which the detection information is recorded, correction of sensor characteristics that have changed over time due to repeated printing by the same image forming apparatus, or sensors of different image forming apparatuses A method for correcting the characteristics will be described with reference to the flowchart of FIG.

  In step S215, a process for correcting the output characteristics of the color sensor 42 at the time of step S211 is started in response to a request from the image forming apparatus or the user.

  In step 216, the color sensor 42 detects the RGB output value of the patch pattern 60 on the transfer material 11. Here, the patch pattern 60 on the transfer material 11 means that the RGB output value has been detected in the past, and the detection information is recorded on the transfer material 11.

  In step S217, the image forming apparatus reads the automatic recognition symbol 62 by the automatic recognition symbol reading unit.

  In step S218, the automatic recognition symbol 62 read in step S217 is converted into an RGB output value.

  In step S219, the color sensor control unit 435 in the image processing unit 43 compares the RGB output value read in step S218 with the RGB output value in step S216.

  In step S220, the color sensor control unit 435 creates a color sensor output correction table based on the difference between the output values compared in step S219, and corrects the output characteristics of the color sensor 42.

  As an effect specific to the second embodiment, it is possible that the user does not need to input detection information.

In the above flow, the automatic recognition symbol 62 is read by the reading unit of the image forming apparatus. However, the automatic reading device connected to the image forming apparatus reads the automatic recognition symbol and sends detection information to the image forming apparatus. good. In this case, there is an effect that it is not necessary to mount an automatic recognition symbol reading unit in the image forming apparatus.
[Third Embodiment]
FIGS. 10A and 10B are flowcharts showing a method for correcting color sensor characteristics using detection information detected in the past as a third embodiment. FIG. 11 is a diagram illustrating an example of a patch pattern and detection information in the color sensor correction method according to the third embodiment.

  In the third embodiment, the detection information is identification information for referring to past detection information stored in the external storage device, and the detection information is recorded by recording the identification information corresponding to the detection information in advance. In the process of recording, the paper is not fed again.

  A color sensor correction method according to the third embodiment will be described with reference to FIGS.

  First, a method for recording detection information and a method for storing detected measurement values in an external storage device will be described with reference to the flowchart of FIG.

  In step S <b> 311, the image forming unit of the image forming apparatus records the identification information 63 on the transfer material 11 other than the patch pattern 60. Here, the identification information 63 may be anything as long as the patch pattern can be specified. For example, a combination of a serial number of the image forming apparatus and a date or a cumulative number printed with the pattern is preferable.

  In step S <b> 312, the color sensor 42 detects the RGB output value of the patch pattern 60.

  In step S313, the image forming apparatus transmits the RGB output value and identification information 63 detected in step S312 to a personal computer connected to the image forming apparatus, and the personal computer stores the RGB output value and identification information 63.

  Up to step S313, recording of the detection information on the transfer material 11 and storage of the RGB output value of the patch pattern 60 and the identification information 63 in step S311 are completed.

  Next, by using a transfer material on which an image to be detected has already been printed and the detection information stored, correction of sensor characteristics that have changed over time due to repeated printing on the same image forming apparatus, or sensors of different image forming apparatuses A method for correcting the characteristics will be described.

  In response to a request from the image forming apparatus or the user, in step S314 in the flowchart of FIG. 10B, processing for correcting the output characteristics of the color sensor 42 at the time of step S312 is started.

  In step S 315, the color sensor 42 detects the RGB output value of the patch pattern 60 on the transfer material 11. Here, the patch pattern 60 on the transfer material 11 is a pattern in which the RGB output values have been detected in the past, and the detection information is stored in the external storage device.

  In step S316, the user inputs the identification information 63 recorded in step S311 to a personal computer connected to the image forming apparatus.

  In step S317, the personal computer transmits the RGB output value specified by the identification information 63 to the image forming apparatus.

  In step S318, the color sensor control unit 435 in the image processing unit 43 compares the RGB output value received from the personal computer in step S317 with the RGB output value in step S315.

  In step S319, the color sensor control unit 435 obtains the difference between the output values compared in step S318, creates a color sensor output correction table from these, and corrects the output characteristics of the color sensor 42.

  As an effect peculiar to the third embodiment, there is no need to re-feed in order to record the detection information.

  Further, although the method of inputting the identification information 63 by the user has been described, the identification information can be the automatic recognition symbol described in the second embodiment. In this case, there is an effect that user input can be omitted.

  As described above, in the first to third embodiments, the embodiment in the color image forming apparatus has been described. However, the same control is possible in the single-color image forming apparatus.

  Further, the detected image includes a standard color chart prepared in advance for sensor correction and the like. It also includes images used by actual users other than detection images such as patch patterns. In this case, since the image to be used and its detection position are not constant, it is necessary to include the detected position information on the transfer material in the detection information.

  Further, the image to be detected may be an already created image fed or may be created by an image forming apparatus immediately before detection. Standard color charts are included in the former. When the latter detected image is created by the image forming apparatus, there is an advantage that it is not necessary to re-feed for detection by performing detection after fixing of the image.

  In the first and second embodiments, the method in which the user re-feeds after detection has been described. However, when recording on the back surface is possible by the transport mechanism in the image forming apparatus, the same transfer material is used. There is also a method of recording on the back side of the. In this case, there is an advantage that it is possible to omit the trouble of refeeding by the user.

  Further, the detection information has been described using the method of recording on the same transfer material as the transfer material on which the image is formed, but there is also a method of recording on a different transfer material. When recording on the same transfer material surface, there is an advantage that the image and its detection information can be managed with only one transfer material. On the other hand, when recording on different transfer materials, recording on the back surface is possible. There is an advantage that it is possible to save the trouble of refeeding even when the transport mechanism is not provided.

  Furthermore, in the present invention, it is very important to store a transfer material on which an image to be detected is printed. It is desirable to store in an environment avoiding strong external light, high temperature and high humidity, which does not cause deformation of the transfer material, image smearing or discoloration. When a storage place is provided in the main body of the image forming apparatus, the detection image storage place may be provided in a place where ultraviolet rays and temperature rise can be avoided, such as the inside of a paper feed cassette or a door. In this case, there is an advantage that the detected image can be prevented from being lost and can be easily taken out when the sensor is corrected.

1 is a diagram illustrating a configuration of a color image forming apparatus according to an embodiment of the present invention. 5 is a flowchart illustrating an example of image processing by the image forming apparatus according to the present exemplary embodiment. It is a flowchart which shows an example of the correction process by a color sensor. It is a figure which shows an example of a density | concentration and chromaticity detection sensor, and a color sensor. It is a figure which shows an example of the transfer material 11 on which the patch pattern 60 was recorded. It is a flowchart which shows the color sensor correction method of 1st Embodiment. It is a figure which shows an example of the patch pattern and detection information in the color sensor correction method of 1st Embodiment. It is a flowchart which shows the color sensor correction method of 2nd Embodiment. It is a figure which shows an example of the patch pattern and detection information in the color sensor correction method of 2nd Embodiment. It is a flowchart which shows the color sensor correction method of 3rd Embodiment. It is a figure which shows an example of the patch pattern and detection information in the color sensor correction method of 3rd Embodiment. It is a figure explaining the correction method of the output characteristic of a color sensor.

Explanation of symbols

11 Transfer materials 21a, 21b Paper feed units 22Y, 22M, 22C, 22K Photosensitive drum (photosensitive member)
23Y, 23M, 23C, 23K Injecting charger 23YS, 23MS, 23CS, 23KS Sleeve 24Y, 24M, 24C, 24K Scanner unit 25Y, 25M, 25C, 25K Toner cartridge 26Y, 26M, 26C, 26K Developer 27 Intermediate transfer member 28a , 28b Transfer roller 29 Cleaning means 30 Fixing section 31 Fixing roller 32 Pressure roller 33, 34 Heater 41 Unfixed toner density detection sensor 42 Density or chromaticity detection sensor (color sensor)
43 Printer controller (image processing unit)
431 Color matching table 432 Color separation table 433 Calibration lookup table 434 Halftone processing 435 such as dither Color sensor control unit 44 Operation panel 45 Personal computer 51 Light emitting element 52 Light receiving element 53 Optical element 54 Light emitting element (white LED)
55 RGB filter 60 Patch pattern 61 Detection information (numerical value)
62 Detection information (automatic recognition symbol)
63 Detection information (identification information)
64 Gray gradation patch with black 65 Process gray gradation patch with YMC

Claims (21)

Detection means for detecting the density or chromaticity of the image formed on the recording medium;
Image forming means for controlling image formation using detection information obtained by the detection means,
An image forming apparatus, wherein the detection information is recorded on a recording medium.   The image forming apparatus according to claim 1, wherein the detection information is a measured value of density or chromaticity of an image detected by the detection unit.   The detection information is identification information corresponding to a measured value of density or chromaticity of an image detected by the detection means, and is recorded in the image forming apparatus or an external storage device connected to the image forming apparatus. The image forming apparatus according to claim 1, wherein:   The image forming apparatus according to claim 1, wherein a recording medium for recording the detection information is the same as a recording medium on which an image is formed.   The image forming apparatus according to claim 1, wherein a recording medium that records the detection information is different from a recording medium on which an image is formed.   5. The image according to claim 4, wherein after the density or chromaticity of the image on the recording medium is detected, the recording medium is conveyed to the image forming unit by a conveying unit to record detection information. Forming equipment.   The image forming apparatus according to claim 4, wherein the detection information is recorded in a portion other than an image formed on a recording medium. Detection means for detecting the density or chromaticity of the image formed on the recording medium;
Comparison means for comparing detection information obtained by the detection means with detection information of the same image detected in the past;
An image forming apparatus comprising: a correction unit that corrects the characteristics of the detection unit using the comparison result.   9. The image forming apparatus according to claim 8, wherein the detection information is a measured value of density or chromaticity of an image detected in the past.   The detection information is identification information corresponding to a measurement value of density or chromaticity of an image detected in the past by the detection unit, and is recorded in the image forming apparatus or an external storage device connected to the image forming apparatus. The image forming apparatus according to claim 8, wherein:   The image forming apparatus according to claim 8, wherein the detection information is input from an image forming apparatus or an external input device connected to the image forming apparatus.   The image forming apparatus according to claim 8, wherein a reading unit that reads detection information recorded on the recording medium is built in or externally connected.   The image forming apparatus according to claim 12, wherein the detection unit also serves as the reading unit.   The image forming apparatus according to claim 8, wherein an operation when detecting an image formed on a recording medium is different from an operation when forming an image on the recording medium.   15. The method according to claim 14, wherein when the image formed on the recording medium is detected as the different operation, a path different from a conveyance path of the recording medium when the image is formed on the recording medium is used. Image forming apparatus.   The image forming apparatus further includes a fixing unit that heats an image and fixes the image on the recording medium. As the different operation, the heating temperature by the fixing unit when detecting the image on the recording medium is changed. The image forming apparatus according to claim 14, wherein the temperature is lower than the temperature.   The image forming apparatus further includes a fixing unit that contacts the image and fixes the image on the recording medium, and as the different operation, when the image on the recording medium is detected, the fixing unit does not contact the image. The image forming apparatus according to claim 14.   The determination unit according to claim 8, further comprising a determination unit that determines whether the detection unit is abnormal based on a difference between detection information by the detection unit and detection information of the same image detected in the past. Image forming apparatus. A control method for an image forming apparatus, comprising: a detecting unit that detects density or chromaticity of an image formed on a recording medium; and an image forming unit that controls image formation using detection information obtained by the detecting unit. There,
A method comprising the step of recording the detection information on a recording medium. A control method for an image forming apparatus comprising a detecting means for detecting the density or chromaticity of an image formed on a recording medium,
A comparison step of comparing detection information obtained by the detection means with detection information of the same image detected in the past;
And a correction step of correcting the characteristics of the detection means using the result of the comparison.   A program for causing a computer of an image forming apparatus to execute the control method according to claim 19 or 20.

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