JP6370091B2 - Image forming apparatus and detection apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms a full-color image by an electrophotographic system, an inkjet system, or the like.

  Japanese Patent Laid-Open No. 2004-228867 forms a single color gradation patch of cyan, magenta, yellow, and black, or a mixed color patch of cyan, magenta, and yellow on the surface of a recording material, and the density or color after fixing by a fixing device. An image forming apparatus for detecting chromaticity is disclosed. Then, the controller feeds back the exposure amount of the image forming unit, the process conditions, the calibration table for correcting the density-gradation characteristics, etc. based on the density or chromaticity of the color after fixing, and the recording material The color density or chromaticity of the output image formed on the surface is corrected. Further, when detecting the density or chromaticity of the color, the white reference member is used and the light reflected by the white reference member is used as a reference.

  Patent Document 2 discloses a small-sized spectral colorimetry device (color sensor) that can be applied to an image forming apparatus. The spectrocolorimeter includes an illumination optical system that illuminates a test object disposed on a test surface, a light guide optical system that guides a reflected light beam from the test object to the spectroscopic optical system, A spectroscopic optical system that obtains a spectral intensity distribution by splitting a target light beam. The light of the illumination optical system reaches the test surface, then passes through the light guide optical system, reaches the spectroscopic optical system, and is received by the light receiving element array.

  The following configurations can be considered with reference to these technologies. A color sensor and a white reference member are arranged to face each other in the sheet conveyance path after fixing. Inside the color sensor, a light source such as a white light emitting diode having a light emission band of approximately 350 nm to 750 nm is disposed. Immediately before the object on which the single-color gradation patch or mixed color patch is formed is conveyed to the sheet conveyance path after fixing, the light is irradiated from the light source to the white reference member, and the reflected light from the white reference member is dispersed. The measured light is measured by an arrayed photoelectric conversion element, and the light source is calibrated. Then, light is emitted from the light source to the object on which the conveyed patch is formed, and the spectral reflectance is calculated.

  Here, the “distance from the light source to the white reference member when calibrating” and the “distance from the light source to the test surface of the recording material when detecting the brightness of the patch” are preferably the same. .

Japanese Patent No. 40654485 JP 2010-276599 A

  However, in practice, the “distance from the light source to the white reference member during calibration” and the “distance from the light source to the test surface of the recording material when detecting the brightness of the patch” are different. Therefore, an error may occur in the brightness of the color calculated by the controller.

In view of the above circumstances, an object of the present invention is to switch a position for detecting a white reference member and a position for detecting a patch.

In order to achieve the above object, an image forming apparatus of the present invention includes a detection unit that detects a detection image formed on a recording material, and a white reference member that is disposed at a position facing the detection unit. The detection means moves to the first position when detecting the detection image, moves to the second position when detecting the white reference member, and detects a movement image having a reflected light amount different from that of the detection image. In this case, the second position is moved from the second position to the first position .

Another image forming apparatus of the present invention includes a detection unit that detects a detection image formed on a recording material, and a white reference member that is disposed at a position facing the detection unit. The detection means moves to a third position when the detection image is detected , and moves to a fourth position when the white reference member is detected by the detection means .

  According to the present invention, the position for detecting the white reference member and the position for detecting the patch can be switched.

1 is a cross-sectional view of an image forming apparatus according to Embodiment 1. FIG. It is sectional drawing of a color sensor. It is a graph which shows the relationship between the wavelength of the light reflected from the test object, and the signal intensity of a line sensor. It is a figure which shows the color patch of the surface of a sheet | seat. It is sectional drawing which shows a mode that a cam rotated and the color sensor retracted | saved from the white reference member. It is a figure which shows trigger patches T1 and T2 and color patches C11 to C23 on the surface of the sheet according to the second embodiment. It is a flowchart which shows the control process of the colorimetry test mode of an engine control part. 6 is a cross-sectional view illustrating a configuration of a color sensor according to Embodiment 3. FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, since the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, there is no specific description. As long as the scope of the invention is not limited to these, it is not intended.

  FIG. 1 is a cross-sectional view of the image forming apparatus 100 according to the first embodiment. An image forming apparatus 100 shown in FIG. 1 is an electrophotographic color image forming apparatus, and its operation will be described by dividing it into a normal print mode and a test mode for executing colorimetry. The image forming apparatus 100 forms yellow (Y), magenta (M), cyan (C), and black (K) color toner images on the surfaces of the four photosensitive drums 50, and the surface of the intermediate transfer belt 55. Is a tandem type color image forming apparatus that forms a full color by superimposing them.

  The image forming apparatus 100 includes an apparatus main body 100A. Inside the apparatus main body 100A, photosensitive drums 50Y, 50M, 50C and 50K as “image carriers” are arranged. Around the photosensitive drums 50Y, 50M, 50C, and 50K, primary charging devices 52Y, 52M, 52C, and 52K, scanning optical devices 51Y, 51M, 51C, and 51K, and developing devices 53Y, 53M, 53C, and 53K are sequentially arranged. Is done.

  The primary charging devices 52Y, 52M, 52C, and 52K uniformly charge the surfaces of the photosensitive drums 50Y, 50M, 50C, and 50K. The scanning optical devices 51Y, 51M, 51C, and 51K expose electrostatic images on the surfaces of the photosensitive drums 50Y, 50M, 50C, and 50K. The developing devices 53Y, 53M, 53C, and 53K develop the electrostatic images formed on the surfaces of the photosensitive drums 50Y, 50M, 50C, and 50K with toner.

  The engine control unit 41 constituting a part of the aforementioned “controller” includes a photosensitive drum 50, a primary charging device 52, a scanning optical device 51, a developing device 53, a primary transfer roller 54, a color sensor 10, and other devices. Controls driving of the internal device of the main body 100A.

  First, the operation in the normal print mode of the image forming apparatus 100 will be described. The surfaces of 50Y, 50M, 50C, and 50K are uniformly charged by primary charging devices 52Y, 52M, 52C, and 52K, and electrostatic images are formed on the surfaces by scanning optical devices 51Y, 51M, 51C, and 51K. . The scanning optical device 51 is connected to a controller 40 serving as an image data processing unit via an engine control unit 41. The controller 40 outputs a signal representing the color of an image sent from an external device such as a computer to form an image. It is converted into a signal that matches the color gamut of the device.

  The scanning optical devices 51Y, 51M, 51C, and 51K apply laser beams LY, LM, LC, and LK modulated based on image information received and processed by the controller 40 to the photosensitive drums 50Y, 50M, 50C, and 50K. Outputs to form an electrostatic image. The developing devices 53Y, 53M, 53C, and 53K develop the above-described electrostatic image with yellow (Y), magenta (M), cyan (C), and black (K) toners to form toner images.

  The intermediate transfer belt 55 is in contact with the photosensitive drums 50Y, 50M, 50C, and 50K, and rotates clockwise by the driving roller 56 in synchronization with the rotation of the photosensitive drums 50Y, 50M, 50C, and 50K. Inside the intermediate transfer belt 55, primary transfer rollers 54Y, 54M, 54C, and 54K are arranged. The primary transfer rollers 54Y, 54M, 54C, and 54K sequentially transfer the toner images formed on the surfaces of the photosensitive drums 50Y, 50M, 50C, and 50K to the intermediate transfer belt 55 by the primary transfer bias applied thereto. . Thus, a color toner image is formed on the surface of the intermediate transfer belt 55.

  On the other hand, a cassette 60 is disposed below the apparatus main body 100A. Sheets P that are recording materials are stacked inside the cassette 60. After the sheet P is fed by the feeding roller 61, the sheet P is conveyed by the conveying roller pair 62 and is conveyed to the registration roller pair 63 whose driving is stopped.

  After the skew is corrected by the registration roller pair 63, the sheet P is conveyed to a secondary transfer unit including a backup roller 58 and a secondary transfer roller 57 at a predetermined timing. The secondary transfer roller 57 transfers the toner image formed on the surface of the intermediate transfer belt 55 to the sheet P by the secondary transfer bias applied thereto. Thereafter, after the toner image is fixed by applying heat and pressure to the surface of the sheet P, the fixing device 64 is discharged outside the apparatus main body 100A by the discharge roller pairs 65 and 66.

  Next, the operation in the test mode for measuring the color image of the sheet P will be described. Assume that the test mode is designated on the operation panel of the image forming apparatus 100 or a personal computer connected to the image forming apparatus 100. Alternatively, it is assumed that the engine control unit 41 automatically executes the test mode based on a detection result such as a change in environment or a change in the apparatus main body 100A.

  The engine control unit 41 generates a test color patch signal from its internal signal generation circuit. Based on the patch signal data, the engine control unit 41 converts the laser beams LY, LM, LC, and LK to the photosensitive drums 50Y, 50M, 50C, Exposure is achieved by firing on a 50K surface. As a result, electrostatic images of color patches are formed on the surfaces of the photosensitive drums 50Y, 50M, 50C, and 50K.

  The test color patch is formed on the surface of the intermediate transfer belt 55 by the same process as the operation in the normal print mode, and then transferred to the sheet P separately conveyed by the secondary transfer roller 57. It is conveyed to the fixing device 64 and fixed on the sheet P.

  The color sensor 10 (the color sensor 30 in the second embodiment) and the white reference member 20 are arranged downstream of the sheet conveyance direction L as the “recording material conveyance direction” from the fixing device 64 that fixes the toner image to the sheet P. .

  FIG. 2 is a cross-sectional view of the color sensor 10. With reference to FIGS. 2 to 4, a method for the color sensor 10 to measure the color patch fixed on the sheet P will be described below. The white reference member 20 is disposed on the left side of the conveyance path 67, and the color sensor 10 is disposed on the right side of the conveyance path 67. In other words, the image forming apparatus 100 includes a conveyance path 67 for the sheet P partitioned between the color sensor 10 and the white reference member 20.

  The color sensor 10 is a sensor for reading chromaticity information of a color patch formed on the surface of a sheet P as a “recording material”, and includes a white LED light source 11, a spectroscopic optical element 12, a line sensor 13, and a light guide. A light body 14 is provided. The white reference member 20 faces the color sensor 10.

  The white LED light source 11 has a light emission distribution over the entire visible light range. The spectroscopic optical element 12 has a reflective diffraction grating surface. The spectroscopic optical element 12 has a function as a so-called prism, and is an element that guides light of a predetermined wavelength to a specific position of the line sensor 13. The line sensor 13 has a large number of photoelectric conversion elements arranged in an array at a pitch of several micrometers. The light guide 14 irradiates the detected surface with the light beam from the white LED light source 11 and guides the reflected light to the spectroscopic optical element 12.

  The line sensor 13 outputs a voltage signal for each pixel based on the intensity of the incident spectral light beam. The AD converter 15 converts the output electric signal into a digital signal for each pixel. The arithmetic processing unit 16 calculates the converted signal. The memory unit 17 stores information calculated by the calculation processing unit 16.

  The color sensor 10 can move to a first position M1 (see FIG. 5) when reading the chromaticity information of the color patch, and a second position M2 when calibrating by irradiating the white reference member 20 with light. It is.

  FIG. 2 shows a state in which there is no sheet P between the color sensor 10 and the white reference member 20 and the color sensor 10 is calibrated, and the color sensor 10 moves in the direction of the arrow J2 to move to the second position. This is a state located at M2. The second position M2 is the position of the color sensor 10 that has approached the white reference member 20.

  As will be described later, in FIG. 5, there is a sheet P between the color sensor 10 and the white reference member 20, and the color sensor 10 reads the chromaticity information of the color patch. It is in a state where it moves in the J1 direction and is located at the first position M1. The first position M1 is the position of the color sensor 10 retracted from the white reference member 20.

  Further, the position of the white reference member 20 does not change between when the color sensor 10 is located at the first position M1 and when it is located at the second position M2. Further, the white reference member 20 is disposed at a position farther from the color sensor 10 than the virtual extension line K of the transport path 67. The virtual extension line K described in FIG. 2 is described virtually, and is actually a portion that is an opening.

  FIG. 3 is a graph showing the relationship between the wavelength of the light reflected from the test object and the signal intensity of the line sensor 13. Each pixel of the line sensor 13 is associated with a corresponding wavelength λ in advance. For this reason, it can be processed as light wavelength-signal intensity data. Therefore, immediately before measuring the color patch formed on the surface of the sheet P, calibration is performed using the white reference member 20 whose spectral reflectance has been measured in advance (correcting the difference in input and output colors to change the color). The method for measuring the color of the color patch will be described in detail below.

  Here, the signal intensity of the line sensor 13 that has detected the white reference member 20, the signal intensity of the line sensor 13 that has detected the color patch, and the signal intensity of the line sensor 13 that has detected the trigger patch T1 are described. When the line sensor 13 detects the signal intensity of the white reference member 20, an individual difference in the spectral distribution of the white LED light source 11 is detected.

  When the line sensor 13 detects the signal intensity of the color patch, the target to be detected is various colors, and the left side in FIG. 3 is red or the like (red is a short wavelength of light). The right-hand side is blue or the like (blue has a long wavelength of light). When the line sensor 13 detects the trigger patch T1, the detection target is black, and the signal intensity of the line sensor decreases and is constant.

  The white LED light source 11 irradiates light to the white reference member 20 facing the color sensor 10. The wavelength-signal intensity spectrum of the reflected light at this time is defined as Wi (λ). Let Wr (λ) be the spectral reflectance when the light source r described later irradiates the white reference member 20 with light in advance.

  The white LED light source 11 irradiates light to the color patch facing the color sensor 10. The wavelength-signal intensity spectrum of the reflected light at this time is Oi (λ). Let Or (λ) be the spectral reflectance when the light source r irradiates the color patch with light.

  The aforementioned wavelength-signal spectrum has a correspondence relationship that the color of this wavelength corresponds to this pixel address of this line sensor 13. When Wi (λ), Wr (λ), Oi (λ), and Or (λ) are defined as described above, Equation (1) is established.

[Equation 1] Or (λ) = {Oi (λ) / Wi (λ)} × Wr (λ) (1)
Here, the light source r is a colorimetric standard illuminant (standard light) described in JIS Z8720 and an auxiliary illuminant D50 in the standard light source.

  When the color sensor 10 measures a color patch, first, the arithmetic processing unit 16 replaces the wavelength λ shown in Expression (1) with the pixel address n. The arithmetic processing unit 16 calculates Oi (n) / Wi (n) for each pixel based on the output signal Wi (n) of the white reference member 20 and the output signal Oi (n) of the color patch measured in advance. Here, n represents the order of each pixel of the line sensor 13.

  Thereafter, the relationship between each pixel of the line sensor 13 and the wavelength associated with this correction method is read from the memory unit 17, and the pixel address n is replaced with the wavelength λ to obtain Oi (λ) / Wi (λ). Thereafter, the value of Wr (λ) stored in the memory unit 17 is read, and the spectral reflectance Or (λ) of the color patch can be obtained according to the equation (1).

  Next, a state when the color sensor 10 is calibrated using the white reference member 20 will be described with reference to FIG. The sheet P is conveyed in the sheet conveyance direction L. The white reference member 20 is disposed at a position recessed from the conveyance path 67 where such a sheet P is conveyed. For this reason, the white reference member 20 is prevented from interfering with the conveyance of the sheet P.

  However, the position where the color patch formed on the surface of the sheet P is detected is slightly different from the position where the white reference member 20 is detected, resulting in an error during color measurement. Therefore, the position of the color sensor 10 is moved toward the white reference member 20 by the rotation of the cam 18, so that the error in the colorimetric position of the color sensor 10 is eliminated.

  In the calibration, after adjusting the light emission amount of the white LED light source 11 to be a predetermined light amount, the correspondence between the pixel address n of the line sensor 13 and the wavelength λ is confirmed, and the wavelength-signal intensity spectrum of the white reference member 20 is confirmed. Measure Wi (n). Calibration using the white reference member 20 is completed by repeatedly transmitting the signal obtained by this measurement to the arithmetic processing unit 16 a plurality of times.

  FIG. 4 is a diagram showing color patches on the surface of the sheet P. As shown in FIG. After this calibration is completed, the sheet P on which the color patches C11, C12, C13, C14... C21, C22, C23 as shown in FIG.

  A trigger patch T1 (predetermined patch) formed of black toner is printed in the vicinity of the front end of the sheet P. Since the color sensor 10 that has measured the color of the white reference member 20 has a large amount of reflected light, the line sensor 13 is charged with a large amount of charge. However, the output level of the line sensor 13 is detected by detecting the trigger patch T1 with black toner. Greatly decreases (see FIG. 3). The engine control unit 41 starts the detection of the color patch with the detection of the trigger patch T1 as a trigger.

  FIG. 5 is a cross-sectional view showing a state where the cam 18 rotates and the color sensor 10 is retracted from the white reference member 20. The color sensor 10 moves from the second position M2 to the first position M1 by detecting the trigger patch T1 formed on the sheet P. That is, when the above-described trigger patch T1 is detected, the color sensor 10 is retracted by the rotation of the cam 18 using this as a trigger, and the color patch on the sheet P is read by the springs 19 arranged above and below the color sensor 10. To move instantly. Therefore, the mode is switched to the mode for measuring the wavelength-signal intensity spectrum Oi (n) of the color patch.

  The color patches are cyan (C), magenta (M), yellow (Y), and black (K) single-color gradation patches and C, M, and Y mixed-color patches, and they are triggered in a predetermined order. Printed after the patch T1. That is, the trigger patch T1 is formed at a position closer to the leading end of the sheet P than the color patches C11 to 23 on the sheet P with respect to the conveyance direction of the sheet P at the position of the color sensor 10.

  At this time, if the signal output from the line sensor cannot be obtained above a certain level, the SN ratio (ratio of signal to noise) is reduced (effective signal ratio is reduced), and sufficient colorimetric accuracy is obtained. It can no longer be obtained. For this reason, the dark color patches C21, C22, and C23 are formed longer than the bright color patches C11, C12, C13, and C14.

  The color sensor 10 can measure the plurality of color patches in order and send them to the arithmetic processing unit 16 to obtain spectral reflectance data Or (λ) corresponding to the number of color patches.

  The spectral reflectance data Or (λ) calculated by the arithmetic processing unit 16 inside the color sensor 10 is sent to the controller 40 via the engine control unit 41 (see FIG. 1) of the apparatus main body 100A. The storage means of the controller 40 includes a color matching table, color separation table, density correction table, and the like used for color conversion, and a data processing unit that converts color information sent from a personal computer into appropriate YMCK data. ing. Therefore, the lighting time of the laser beam is set as the video data corrected based on the spectral reflectance data Or (λ).

  FIG. 6 is a diagram illustrating trigger patches T1 and T2 and color patches C11 to C23 on the surface of the sheet P according to the second embodiment. As shown in FIG. 6, the second embodiment is different from the first embodiment in that a trigger patch T <b> 2 (predetermined patch) indicating the end of color measurement is provided at the rear end of the sheet P. As a result, the color sensor 10 moves to the white reference member 20 side again from the mode in which the color sensor 10 detects the trigger patch T2 and measures the color patch, and switches to the calibration mode.

  This is due to the following reason. If the white LED light source 11 of the color sensor 10 is continuously turned on, the light emission amount may slightly vary. In addition, a slight change may occur in the correspondence between the pixel address n of the line sensor 13 and the wavelength λ due to the heat of the sheet P that has passed through the fixing device 64. In order to avoid this, it is preferable to perform calibration again using the white reference member 20 after the color measurement.

  Further, the number of color patches formed on the sheet P is not limited to one, and it is possible to correct with higher accuracy by measuring colors using a number of color patches formed by a plurality of sheets. This is more effective in reducing errors in calibration using the white reference member 20 between sheets (paper intervals) where a plurality of sheets P are conveyed.

  As described above, the trigger patch formed at the leading edge or the trailing edge of the sheet P on which the color patch is formed is detected, the color sensor 10 is moved, and the calibration mode and the colorimetry mode are switched. .

  In short, calibration is performed using the white reference member 20 before and after the sheet P in FIG. 6 is conveyed. The first result of spectral reflectance data Or (λ) obtained using the white reference member 20 calibrated and detected before the sheet P, and the white reference member 20 calibrated and detected after the sheet P The second result of the spectral reflectance data Or (λ) obtained by use is averaged. The arithmetic processing unit 16 sets the lighting time of the laser light as the corrected video data based on the average value (averaged data) of the first result and the second result.

  Alternatively, the first result of the wavelength-signal spectrum Wi (λ) obtained using the white reference member 20 calibrated and detected before the sheet P and the white reference member calibrated and detected after the sheet P The second result of the wavelength-signal spectrum Wi (λ) obtained using 20 is averaged. Then, the arithmetic processing unit 16 calculates the spectral reflectance Or (λ) of the color patch based on the average value (averaged data) of the first result and the second result. Then, the lighting time of the laser beam may be set as video data corrected based on this.

  From this, the following can be said. The color sensor 10 and the color sensor 30 irradiate the white reference member 20 with light before the sheet P on which the color patch is formed and after the sheet P on which the color patch is formed. Produces an output signal. The engine control unit 41 changes the time that the scanning optical device 51 irradiates the photosensitive drum 50 based on the average value of the output signal before the sheet P is conveyed and the output signal after the sheet P is conveyed. To do.

  FIG. 7 is a flowchart showing a control process in the colorimetric test mode of the engine control unit 41. The control subject is not limited to the engine control unit 41 and may be another control system. With reference to FIG. 7, a process in which color patches are formed on a plurality of sheets P and the color sensor 10 repeatedly performs calibration and color measurement will be described.

  When the engine control unit 41 receives an instruction of the colorimetric test mode from the controller 40, the image forming unit forms a preset color patch and trigger patch on the photosensitive drum 50 (S1). In synchronization with this, the engine control unit 41 feeds the sheets P from the cassette 60 in the order of the set number of sheets (S2). After the step S1 and the step S2, the engine control unit 41 transfers the color patch and the trigger patch onto the sheet P and passes them through the fixing device 64 for fixing (S3). The engine control unit 41 sequentially conveys the sheet P to a position facing the color sensor 10 (S4).

  The engine control unit 41 starts preparation for calibration by the color sensor 10, rotates the cam 18, and sets the color sensor 10 to move toward the white reference member 20 (S5). When the color sensor 10 reaches the second position M2, the engine control unit 41 sets the light amount of the white LED light source 11 and acquires the output signal Wi (n) of the white reference member 20 a plurality of times (S6).

  In the engine control unit 41, the color sensor 10 detects the trigger patch T1 formed at the leading end of the sheet P (S7). The engine control unit 41 rotates the cam 18 so that the color sensor 10 moves back to the color measurement position (S8). The engine control unit 41 starts color measurement of the color patch from the set time, acquires the output signal Oi (n) for each color patch, and sequentially transmits it to the arithmetic processing unit 16 in the color sensor 10 (S9). ).

  In the engine control unit 41, the color sensor 10 detects the trigger patch T2 formed on the rear end of the sheet P (S10). The engine control unit 41 rotates the cam 18 again to move the color sensor 10 to the calibration position (S11), and obtains the output signal Wi (n) of the second white reference member 20 (S12). ), An error detection and averaging process is performed by the arithmetic processing unit 16.

  The engine control unit 41 determines whether the set number of colorimetry has been completed (S13). If the result of S13 is YES, the engine control unit 41 transmits the result calculated by the arithmetic processing unit 16 inside the color sensor 10 to the engine control unit 41 and the printer controller 40 (S14). If the result of S13 is NO, the engine control unit 41 returns to the process of S7.

  FIG. 8A illustrates the configuration of the color sensor 30 according to the third embodiment, and is a cross-sectional view illustrating how the white reference member 21 approaches the color sensor 30 and calibration is performed. FIG. 8B shows a configuration of the color sensor 30, and is a cross-sectional view showing a state in which the white reference member 21 is retracted from the color sensor 30 and the color sensor 30 detects a color patch.

  The manner in which the white reference member 21 is moved will be described with reference to FIG. As the white reference member 21 shown in FIG. 8, a white tile or the like in which a white glaze (Yuyaku / Wagusuri) is applied to the surface layer of a ceramic tile is often used.

  However, the white reference member 21 may alternatively be a white plastic material in which a white glaze is applied to the surface layer of the plastic material. When this plastic material is used, the white reference member 21 in this case can be easily moved because it can be molded into a light and complicated shape. The white reference member 21 is moved by a movable part 24 such as a solenoid.

  That is, the detection surface 23 of the white reference member 21 is disposed at a position farther from the color sensor 30 than the virtual extension line K of the transport path 67 when the detection surface 23 is located at the third position M3. In addition, the detection surface 23 of the white reference member 21 is disposed at a position that protrudes from the virtual extension line K of the transport path 67 to the color sensor 30 when the detection surface 23 is positioned at the fourth position M4.

  The color sensor 30 is fixed to the plate 30X by screws 39, and at the time of calibration, the white reference member 21 moves toward the color sensor 30 and is disposed at a position equivalent to the color patch on the surface of the sheet P. . That is, the position of the color sensor 30 does not change between when the white reference member 21 is located at the third position M3 and when it is located at the fourth position M4.

  The operation of the white reference member 21 will be described in detail as follows. FIG. 8A shows a state where there is no sheet P between the color sensor 30 and the white reference member 21, and the color sensor 30 is calibrated, and the color sensor 30 is located at the fourth position M4. State. The fourth position M4 is a position when the color sensor 30 performs calibration by irradiating light. The fourth position M4 is the position of the white reference member 21 that is close to the color sensor 30.

  Further supplementation is as follows. The sheet P is conveyed to the optical path of the white LED light source 11. The color sensor 30 detects the trigger patch T1 at the leading end of the sheet P (upper part in FIG. 8A). As soon as it is detected, the white reference member 21 moves in the direction of arrow J3 and retracts to the third position M3 as shown in FIG. 8B.

  FIG. 8B shows a state where the sheet P is between the color sensor 30 and the white reference member 21, and the color sensor 30 reads the chromaticity information of the color patch. This is a state located at the third position M3. The third position M3 is a position when the white reference member 21 reads the chromaticity information of the color patch by the color sensor 30. The third position M3 is the position of the white reference member 21 retracted from the color sensor 30.

  The white reference member 21 is movable to the third position M3 and the fourth position M4. The white reference member 21 moves from the fourth position M4 to the third position M3 when the color sensor 30 detects the trigger patch T1 formed on the sheet P.

  As described in the first embodiment and the second embodiment, the color sensor 30 has a line after the white light source 81 is adjusted to have a predetermined light amount when the white reference member 21 is in the fourth position M4. The correspondence between the pixel address n of the sensor 33 and the wavelength λ is confirmed, and the wavelength-signal intensity spectrum Wi (n) of the white reference member 21 is measured a plurality of times.

  Further, since the white reference member 21 is configured to protrude from the conveyance path 67 of the sheet P, the white reference member 21 has an inclined portion 22 formed with a gently inclined surface so as not to prevent the conveyance of the sheet P. For this reason, the sheet P is conveyed to the detection position of the color sensor 30 without contacting the detection surface 23 of the white reference member 21. Since the trigger patch T1 is printed on the leading edge of the sheet P, the white reference member 21 is quickly retracted in the direction of the arrow when the color sensor 30 detects the trigger patch T1.

  The tension roller 68 is disposed upstream or downstream in the sheet conveyance direction L of the color sensor 30 to urge the sheet P toward the conveyance path 67 in order to suppress the fluttering of the sheet P when the sheet P is conveyed. .

  In the first to third embodiments, the color sensor of the spectroscopic optical element 12 has been described. However, the present invention is not limited to this configuration. That is, for example, a color sensor having a configuration using three or more light sources having different emission spectra such as red (R), green (G), and blue (B) as the light source may be used. This uses the fact that the same function as using a white light source by combining the light of red, green, and blue light sources occurs.

  Alternatively, for example, a color sensor having a configuration in which filters having different spectral transmittances such as red (R), green (G), and blue (B) are formed on a light receiving element using a white light source may be used. This utilizes the fact that the spectral characteristics of the color patch can be calculated by detecting the amount of light transmitted through each filter. Even in the case of these configurations, the same effects as in the first to third embodiments can be obtained.

  According to the configurations of the first to third embodiments, “the distance from the light source when calibrating to the white reference member 20 (white reference member 21)” and “the test of the sheet P from the light source when detecting the brightness of the patch” The deterioration of the state of the white reference member 20 can be suppressed while making the “distance to the surface” substantially the same.

10 color sensor 20 white reference member 100 image forming apparatus M1 first position M2 second position T1 trigger patch P sheet (recording material)

Claims (14)

Detection means for detecting a detection image formed on the recording material;
A white reference member disposed at a position facing the detection means;
With
The detection means moves to a first position when detecting the detection image, and moves to a second position when detecting the white reference member, and detects a movement image having a reflected light amount different from that of the detection image. In this case , the image forming apparatus moves from the second position to the first position . The detecting means moves from the first position to the second position when detecting a moving image having a reflected light amount different from that of the detecting image after detecting the detecting image. Item 2. The image forming apparatus according to Item 1 . The first position is a position retracted from the white reference member, the second location, to claim 1 or 2, characterized in that than the first position is a position close to the white reference member The image forming apparatus described. And when said detecting means is positioned at the first position, in the case located in the second position, any one of claims 1 to 3, wherein the position of the white reference member is the same The image forming apparatus described in 1. A recording material conveyance path partitioned between the detection means and the white reference member;
The white reference member, the image forming apparatus according to any one of claims 1 to 4, characterized in that it is located away from the detection means than the virtual extended line of the conveying path. Detection means for detecting a detection image formed on the recording material;
A white reference member disposed at a position facing the detection means;
A recording material conveyance path defined between the white reference member and the detection means;
With
The white reference member, when said third position when said detecting image by detecting means is detected, the white reference member by said detection means is detected is moved to the fourth position, and the third When located at a position, it is further away from the detection means than the virtual extension line of the conveyance path, and when located at the fourth position, it is closer to the detection means than the virtual extension line of the conveyance path. Image forming apparatus. The white reference member, if the is detecting image and the moving image is different in the amount of reflected light is detected by said detecting means, claim, characterized in that to move to the third position from the fourth position 6 The image forming apparatus described in 1. Moving said white reference member, when said from said detecting image after the detection image is detected by the detection means moving images with different amount of reflected light is detected, the fourth position from the third position the image forming apparatus according to claim 6 or 7, characterized in that. It said third position, said a position retracted from the detection means, the fourth position may be any of claims 6 to 8, characterized in that than the third position is a position close to the detection means 2. The image forming apparatus according to item 1. The position of the said detection means is the same in the case where the said white reference member is located in the said 3rd position, and the case where it is located in the said 4th position, The any one of Claim 6 thru | or 9 characterized by the above-mentioned. The image forming apparatus described in 1. The detection means irradiates the white reference member with light at least before the recording material on which the detection image is formed is conveyed and after the recording material on which the detection image is formed is conveyed. Generating an output signal and calculating the spectral reflectance Or (λ) of the detection image based on the data obtained by averaging the wavelength-signal intensity spectra Wi (λ) of the plurality of white reference members. the image forming apparatus according to any one of claims 1 to 10,. It said sensing means and said white reference member, according to any one of claims 1 to 11, characterized in that of the fixing device for fixing the toner image on a recording material is disposed downstream of the recording material conveyance direction Image forming apparatus. A light emitting means for emitting light;
A light receiving means for receiving light emitted from the light emitting means;
A white reference member that reflects the light emitted from the light emitting means,
The light emitting means and the light receiving means move to the first position when detecting the detection image formed on the recording material, and move to the second position when detecting the white reference member, and are reflected from the detection image. A detection apparatus that moves from the second position to the first position when moving images with different amounts of light are detected. Light emitting means for emitting light, and detecting means having a light receiving means, a for receiving the light emitted from the front Symbol emitting means,
A white reference member that reflects light emitted from the light emitting means;
With
The white reference member, if the third position when the detection image formed on a recording material by said detecting means is detected, the white reference member is detected is moved to the fourth position, and the second When it is located at the third position, it is farther from the detection means than the virtual extension line of the recording material conveyance path defined between the white reference member and the detection means, and when it is located at the fourth position. The detection apparatus characterized by being closer to the said detection means than the virtual extension line of the said conveyance path .

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