JP2011170053A - Image-forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image-forming device which corrects colors with high accuracy including surface reflection light quantity of a color image. <P>SOLUTION: An image-forming part 3 forms a color image of a predetermined test pattern to be output to a paper sheet. The image-forming part 3 includes an image-reading part (A) which detects the color and surface reflection light quantity of the color image of the test pattern which has been output to the paper sheet in the image-forming part 3. Then, the image-reading part (A) detects the color and surface reflection light quantity of the color image of the test pattern which has been output to the paper sheet, and, on the basis of the detected color and surface reflection light quantity of the color image of the test pattern, the image-forming conditions in the image-forming part 3 are adjusted. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or an inkjet.

  Conventionally, as this type of image forming apparatus, there is an apparatus that copies an image of an original and outputs it to a recording member such as transfer paper. For example, in an image forming apparatus such as a digital copying machine, an image such as an original is scanned by using an image sensor such as a CCD (Charge Coupled Device), and is converted into an electrical signal and processed by a laser printer, A copy image is obtained by printing and recording using an image output device such as an ink jet printer or a thermal transfer printer. As described above, there are various types of image output devices such as laser printers, ink jet printers, thermal transfer printers, etc., but laser printers using the electrophotographic process method have high speed, high resolution, and plain paper. It has advantages such as being usable, and is used in high-end copying machines or printers.

  In an image forming apparatus that outputs a copy of the conventional image, it is necessary to copy an image that is faithful to the read image. However, since the image output apparatus used in the image forming apparatus has different recording characteristics depending on lots and environments, and also varies with time, the fidelity of the copied image with respect to the original image or the input image is impaired. This fidelity is particularly severe in an image that requires gradation such as a photographic image, and when a color image is formed, a quality much higher than that of a monochrome image is required.

  For this reason, it is necessary to adjust the image processing conditions of the image forming apparatus so that it can be reproduced faithfully. In this adjustment work, the process of correcting the image processing conditions to form a copy image and confirming the fidelity of the image is repeated to the satisfaction, so that it takes time and the adjustment result varies depending on the operator. It required skill. Therefore, in order to automate this work, a predetermined test pattern is output from the image output device, and the test pattern image is read by the image input device, so that the recording characteristics of the image output device are detected, and the optimum image processing conditions There has been proposed a color calibration (color correction) method for automatically setting.

  For example, a test pattern in which patches of four colors CMYK (cyan, magenta, yellow, and black) in which the image area ratio and the image density are changed in stages is output, and the test pattern image is read by the image input device. There has been proposed a technique for detecting the gradation characteristics of the current image output apparatus, calculating γ correction data for correcting the gradation characteristics to a predetermined gradation characteristic, and setting the γ correction data in the γ conversion circuit.

  In addition, the full color machine is designed so as to have an appropriate gloss in order to give the output image depth and luxury. The glossiness is determined by the material and melting point of the toner, the material and temperature of the fixing roller, etc., but the temperature / humidity of the environment, the paper thickness / surface property of the recording paper, the toner adhesion amount, and the nip width adjustment of the fixing roller For example, even if the glossiness is designed to be 30%, it may vary up to 20% in the vertical direction.

  The change in glossiness means that the surface shape of the toner changes, and naturally the color is affected. When detecting the color, as shown in FIG. 17A, if the unevenness of the toner surface shape is large, the surface diffuse reflection light becomes large, and the light that has passed through the toner and reflected from the paper is reflected from the toner surface. Since the reflected light is added, the detected brightness is high and the saturation and density are low. Conversely, if the unevenness of the toner surface shape is small, the surface diffuse reflection light becomes small as shown in FIG. 17B, and the surface reflection light is not added to the light that has passed through the toner and reflected from the paper. Decreases, and saturation and density increase.

  That is, the image input device that should read the test pattern and detect the color of the pattern is affected by the surface shape of the toner. For this reason, color calibration cannot perform proper color correction without considering the toner surface state as described above. Specifically, when color calibration is performed with the influence of the surface shape ignored, if the density value is smaller than the standard density value (target density value), for example, the density value is increased. In order to correct, an adjustment is made to increase the toner adhesion amount on the recording member. Here, there is no problem as long as the surface shape is always constant, but if the unevenness of the toner surface shape of the test pattern patch is large due to the above-mentioned various variations, the adhesion will occur even though the density value is small. It will be corrected by increasing the amount. Therefore, there is a possibility that the gradation is crushed on the high image area ratio side (low brightness side) of the image that is actually output.

As described above, when the color of the output image varies due to the above-described various variations, it is necessary to perform color correction in consideration of whether the toner surface condition varies or the toner adhesion amount varies. That is, there is a problem that the following two points must be performed in order to perform color calibration with high accuracy.
(1) To correct fluctuations in the toner adhesion amount on the recording member (paper).
(2) To correct fluctuations in the amount of reflected light on the surface of the toner.

  Conventionally, in order to solve the above-described problem, an image forming apparatus that performs gradation correction in consideration of the influence of a change in glossiness and a change in toner adhesion amount has been proposed (see Patent Document 1). In this image forming apparatus, the relationship between the gloss level, the color, and the toner adhesion amount (color material amount) is obtained in advance, and the test pattern image data read by the image reading unit is detected by the gloss level detection unit. The image processing conditions of the image processing means are adjusted according to the analysis result.

  There has also been proposed a color image reproduction system that performs tone correction by predicting in advance the influence of unnecessary light components contained in reflected light of an image (see Patent Document 2). In this color image reproduction system, the relationship between unnecessary light components, color, and toner adhesion amount (color material amount) is obtained in advance, and the influence of unnecessary light components included in the reflected light of the copied image is predicted in advance. The gradation of the image signal after color correction is corrected, and a duplicate image is output based on the corrected image signal.

  However, in the image forming apparatus disclosed in Patent Document 1 and the color image reproduction system disclosed in Patent Document 2, the relationship between the enormous glossiness or unnecessary light component, color, and toner adhesion amount (color material amount) must be measured in advance. Therefore, troublesome work is required.

  Further, as a result of the study by the present inventors, it is not strictly the glossiness calculated based on the specularly reflected light from the document that strictly affects the color of the output image, but the observation of the person actually viewing the output image It was found to be the surface reflected light component from the toner at an angle.

  The image forming apparatus of Patent Document 1 mainly controls the variation in the toner adhesion amount on the recording member (paper), and there is no control for correcting the surface reflected light amount. Remains, and there is a problem that an image with high accuracy and color correction having a target gradation is not output indefinitely.

  Further, the “unnecessary light component” considered in the correction of the system of Patent Document 2 is not clearly defined, and there remains a problem that the method for obtaining the unnecessary light component is not clearly described.

  The present invention has been made under the above background, and an object of the present invention is to provide an image forming apparatus capable of performing highly accurate color correction including the amount of surface reflection of a color image.

In order to achieve the above object, the invention according to claim 1 is an image reading unit for reading an image, and a color image forming unit that forms a color image based on image data read by the image reading unit and outputs the color image to a recording member. And an image forming condition adjusting means for adjusting an image forming condition of the color image forming means, wherein the color image forming means forms a color image of a predetermined test pattern to form a recording member And detecting means for detecting the color of the color image of the test pattern output to the recording member by the color image forming means and the amount of reflected light on the surface, and the image forming condition adjusting means is the detection means. Adjusting the image forming conditions of the color image forming means based on the color of the color image of the test pattern detected by the means and the amount of reflected light on the surface. Is shall.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the detecting unit detects a spectral reflectance of an image of the test pattern.
According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect, the detection unit includes an illumination unit that illuminates an image to be detected, and a light receiving unit that receives reflected light from the detection target, The illumination means has a polarization element capable of switching the polarization direction in the optical path of the illumination light, and the light receiving means has a polarization element capable of switching the polarization direction in the light path of the light reception. It is characterized by.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the detection unit includes an illuminating unit that illuminates an image to be detected, and two light receiving units that receive reflected light from the detection target. The illumination means has a polarizing element in the optical path of the illumination light, and one of the two light receiving means is in the optical path of the received light with respect to the polarization element of the optical path of the illumination light. A polarizing element having the same polarization direction, and the other light receiving means has a polarizing element in a direction perpendicular to the polarizing element in the optical path of the illumination light in the light receiving optical path. To do.
According to a fifth aspect of the present invention, in the image forming apparatus of the third or fourth aspect, the surface reflected light amount is such that the polarization direction of the polarizing element of the illumination unit and the polarization direction of the polarizing element of the light receiving unit are in the same direction. This is a value calculated based on a value obtained by subtracting the detected light amount from the detected light amount under the condition that the polarization direction of the polarizing element of the illumination unit and the polarization direction of the polarizing element of the light receiving unit are orthogonal to each other. It is characterized by this.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the adjustment of the image forming condition by the image forming condition adjusting unit includes adjustment of γ correction for gradation correction. It is a feature.
According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the color image forming unit includes a fixing device that fixes an image formed on the recording member, and the detection unit includes: It is arranged downstream of the fixing device in the recording member conveyance direction.
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the color image forming unit includes a fixing device that fixes an image formed on the recording member, and the image forming condition adjustment The means is characterized in that the fixing condition of the fixing device is adjusted based on the amount of surface reflected light detected by the detecting means.
According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the image reading unit is also used as the detection unit.
A tenth aspect of the present invention is the image forming apparatus according to any one of the first to ninth aspects, further comprising test pattern data generating means for generating predetermined test pattern data, wherein the color image forming means is the test pattern data generating means. A color image of the test pattern is formed on the basis of the test pattern data generated in step 1 and output to a recording member.
According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects of the present invention, the color image forming unit is configured to store the test pattern based on test pattern data obtained by reading a test pattern document by the image reading unit. A color image is formed and output to a recording member.

  In the image forming apparatus of the present invention, a color image of a predetermined test pattern is formed and output to a recording member, and the color of the color image of the test pattern output to the recording member and the surface reflected light amount are detected. The image forming conditions of the color image forming means are set so that the detection result of the color image of the test pattern is a predetermined color and the detection result of the surface reflection light amount of the color image of the test pattern is a predetermined light amount. Can be adjusted.

  According to the present invention, it is possible to adjust the image forming conditions so that the detection results of the color image and the surface reflected light amount of the test pattern each have a predetermined color and light amount. It is possible to perform highly accurate color correction.

1 is a schematic configuration diagram illustrating an example of an overall configuration of an image forming apparatus according to a first embodiment of the present invention. Explanatory drawing which expanded a part of the image forming apparatus. The graph which shows the relationship between glossiness and surface reflectance. FIG. 2 is a schematic configuration diagram illustrating an example of an overall configuration of an image reading unit of the image forming apparatus. Explanatory drawing which shows the bottom face of the image reading part. FIG. 3 is a block diagram showing an example of a color correction process flow in the image forming apparatus. 6 is a flowchart illustrating an example of a flow of color correction processing in the image forming apparatus. Explanatory drawing for demonstrating (gamma) characteristic. Explanatory drawing which shows the example of a test pattern output. FIG. 5 is a schematic configuration diagram illustrating an example of an overall configuration of an image reading unit of an image forming apparatus according to a second embodiment of the present invention. Explanatory drawing which shows the bottom face of the image reading part. 6 is a flowchart illustrating an example of a flow of color correction processing in the image forming apparatus. FIG. 10 is a schematic configuration diagram illustrating an example of an overall configuration of an image forming apparatus according to a third embodiment of the present invention. FIG. 10 is a schematic configuration diagram illustrating an example of an overall configuration of an image forming apparatus according to a fourth embodiment of the present invention. FIG. 2 is a schematic configuration diagram illustrating an example of an overall configuration of a scanner unit of the image forming apparatus. 6 is a flowchart illustrating an example of a flow of color correction processing in the image forming apparatus. (A) And (b) is explanatory drawing for demonstrating the surface reflected light of a toner, respectively.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a schematic configuration diagram showing the overall configuration of the image forming apparatus according to the first embodiment of the present invention, and FIG. 2 is an enlarged explanatory view of a part thereof. This image forming apparatus is a tandem type full-color image forming apparatus adopting an intermediate transfer method, and a color correction image reading unit A for color calibration as a detecting means capable of detecting the color of an image and the amount of reflected light on the surface. A scanner unit 2 as an image reading unit that reads an image of a document for forming a copy image, an image forming unit 3 as an image forming unit that forms an image on a recording member (sheet), and an image forming unit 3 Are provided with a paper supply section 4 for supplying paper as a recording member and a paper discharge section for discharging the paper after image formation.

  The scanner unit 2 reads an image of a document set on a transparent document table, for example, a contact glass. For example, an optical scanning system including a lamp, a mirror, and a carriage, and an optical scanned by the optical scanning system. A lens system that forms an image and an image reading sensor such as a CCD that receives an optical image formed by the lens system and converts it into an electrical signal are provided.

  The image forming unit 3 includes a plurality of image forming units 10 (10Y, 10M, 10C, 10K) on which toner images of respective color components are formed by electrophotography. Further, the image forming unit 3 sequentially transfers (primary transfer) and holds each color component toner image formed by each image forming unit 10 and the overlapping toner transferred onto the intermediate transfer belt 15. And a secondary transfer section 20 that collectively transfers (secondary transfer) the image onto a sheet P as a recording member (sheet). Further, the image forming unit 3 includes a fixing unit 46 as a fixing unit that fixes the secondary transferred image on the paper P. In addition, the image forming unit 3 outputs a control unit 40 as a control unit that controls the operation of each device (each unit) and an image output from an external device such as the scanner unit 2 as an image reading unit or a computer device (not shown). An image processing unit 44 that creates data for image formation based on the data. In this embodiment, each image forming unit 10Y, 10M, 10C, 10K, the intermediate transfer belt 15, the secondary transfer unit 20, and the like constitute a color image forming unit (color image forming unit). Further, the image forming condition adjusting means for adjusting the image forming conditions of the image forming unit 3 can be configured by at least one of the control unit 40 and the image processing unit 44. Further, the test pattern data generating means for generating predetermined test pattern data can be constituted by the image processing unit 44, for example.

  Each image forming unit 10 (10Y, 10M, 10C, 10K) in FIG. 2 includes a photosensitive drum 11 as a latent image carrier that rotates in the direction of arrow α, and a photosensitive drum provided around the photosensitive drum 11. A charger 12 as a charging means for charging 11 to a predetermined potential; and a laser exposure device 13 (an exposure beam in the figure) as an optical writing means (exposure means) for writing an electrostatic latent image on the photosensitive drum 11. And a developing device 14 as developing means for accommodating each color component toner and visualizing the electrostatic latent image on the photosensitive drum 11 with the toner. Further, around the photosensitive drum 11, a primary transfer roll 16 as a primary transfer unit that transfers each color component toner image formed on the photosensitive drum 11 to an intermediate transfer belt 15 as an intermediate transfer member, a photosensitive drum. An electrophotographic device such as a drum cleaner 17 as a cleaning means for removing the residual toner on 11 is also provided.

  The intermediate transfer belt 15 is circulated and driven at various speeds in the β direction shown in FIG. 2 by various rolls. As these various rolls, a drive roll 31 that is driven by a constant speed drive motor (not shown) to circulate and drive the intermediate transfer belt 15, and an intermediate transfer belt that extends linearly along the arrangement direction of the photosensitive drums 11. 15, a support roll 32 that supports the intermediate transfer belt 15, a tension roll 33 that functions as a correction roll that applies a constant tension to the intermediate transfer belt 15 and prevents the intermediate transfer belt 15 from meandering, and a backup provided in the secondary transfer unit 20. A roll 22 and an idle roll 34 provided downstream of the secondary transfer unit 20 in the transport direction of the intermediate transfer belt 15 are provided.

  A voltage having a polarity opposite to the charged polarity of the toner is applied to each primary transfer roll 16 provided inside the intermediate transfer belt 15 that faces the respective photosensitive drums 11 and extends linearly. As a result, the toner images on the respective photosensitive drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15 to form toner images superimposed on the intermediate transfer belt 15.

  The secondary transfer unit 20 includes a secondary transfer roll 21 disposed on the toner image carrying surface side of the intermediate transfer belt 15, a backup roll 22, and the like. The backup roll 22 is disposed on the back side of the intermediate transfer belt 15 to constitute a counter electrode of the secondary transfer roll 21, and a metal power supply roll 23 to which a secondary transfer bias is stably applied is disposed in contact with the backup roll 22. ing.

  Further, on the downstream side of the secondary transfer portion 20 of the intermediate transfer belt 15, the intermediate transfer belt 15 is disposed so as to face the drive roll 31, and residual toner on the intermediate transfer belt 15 after the secondary transfer or A belt cleaner 35 is provided as an intermediate transfer member cleaning unit that removes paper dust and cleans the surface of the intermediate transfer belt 15 so as to be able to contact with and separate from the intermediate transfer belt 15. On the other hand, on the upstream side of the yellow image forming unit 10Y, a reference sensor (home position sensor) as a reference signal generating means for generating a reference signal serving as a reference for matching the image forming timing in each image forming unit 10 41 is arranged. Further, an image density sensor 42 as density detecting means for adjusting the image quality of each color is disposed on the downstream side of the black image forming unit 10K. The reference sensor 41 recognizes a predetermined mark provided on the back side of the intermediate transfer belt 15 and generates a reference signal. Each image forming unit 10 is instructed by an instruction from the control unit 40 based on the recognition of the reference signal. (10Y, 10M, 10C, 10K) are configured to start image formation. Further, a temperature / humidity sensor 47 as an environment detection unit is disposed inside the intermediate transfer belt 15.

  The fixing unit 46 in FIG. 2 fixes the toner image on the paper P by heating and pressing. In the present embodiment, the fixing unit 46 includes a heating roll 46a serving as a heating member disposed opposite to the image forming surface of the paper P, and a pressing member serving as a pressing member that is disposed in pressure contact with the heating roll 46a to form a fixing nip. A pressure belt 46b and a halogen lamp 46c as a heating source built in the heating roll 46a are provided.

  On the other hand, the paper supply unit 4 conveys each paper P stored in the first tray 50, the second tray 51, and the third tray 52 through a predetermined path. In the vicinity of each of the trays 50 to 52, feed rolls 53, 54, and 55 corresponding to the trays 50 to 52 are disposed. Each of the feed rollers 53 to 55 nips the paper P separated and taken out one by one from the corresponding trays 50 to 52 and temporarily stops the paper P on the paper transport path, and at the timing based on a predetermined start signal, the paper transport direction The sheet P is sent out to the downstream side. Further, an operation panel 56 operated by the user and an input keyboard 56 a are disposed adjacent to the operation panel 56 in the vicinity of the scanner unit (image reading unit) 2 above the paper supply unit 4. The power source 43 of the full-color image forming apparatus 1 is disposed below the third tray 52. In this embodiment, each tray number (number assigned to the first tray 50, the second tray 51, and the third tray 52) is stored in the tray using the operation panel 56, the keyboard 56a, and the like. The input of the type (for example, basis weight, presence / absence of coat layer, type of coat layer, etc.) of the sheet P to be received is accepted. This content is stored in a memory (not shown), and when a predetermined tray number is input on the operation panel 56 and the keyboard 56a, information about the attributes of the paper P stored in the corresponding tray is displayed. It has become so. In the present embodiment, the operation panel 56 and the keyboard 56a function as an input reception unit, a selection reception unit, and a reception unit.

  Subsequently, a basic image forming operation of the tandem type full color image forming apparatus according to the present embodiment will be described. First, when an image of a document is read by the scanner unit 2, a toner image is formed by the image forming unit 3 based on an image signal obtained thereby. In the image forming unit 3, while rotating the four photosensitive drums 11, yellow, magenta, cyan, black on the surface of each photosensitive drum 11 by the corresponding charger 12, laser exposure device 13, and developing device 14. The toner image is formed. The toner images of the respective colors formed in this way are sequentially transferred onto the intermediate transfer belt 15 by the primary transfer roll 16. As a result, a multicolor (full color) toner image is formed on the intermediate transfer belt 15 by superimposing four color toner images. The toner image formed on the intermediate transfer belt 15 is sent to the secondary transfer unit 20 while being carried on the intermediate transfer belt 15.

  On the other hand, when the paper P in the tray selected by the user using the operation panel 56 or the paper P in the tray selected by the automatic selection function, the toner image on the intermediate transfer belt 15 reaches the secondary transfer unit 20. For example, when the selected tray is the first tray 50, the paper P sent out by the sending roll 53 joins via the first paper transport path R1. After being sent to the transport unit 58 and further corrected by the posture correction unit 60 via the second paper transport path R2, it is sent to the secondary transfer unit 20 by the registration roll 61.

  In the secondary transfer unit 20 of the image forming unit 3, the toner image (full color image) carried on the intermediate transfer belt 15 is collectively transferred (secondary transfer) onto the paper P by the secondary transfer roll 21. Thereafter, the paper P on which the toner image has been transferred is sent to the fixing unit 46 by the belt conveyance unit 45, and after being heated and pressurized and fixed, it is placed on the discharge tray 57 of the paper discharge unit via the paper discharge path R3. Discharged.

Next, adjustment of image forming conditions based on the detection result of the color of the color image of the test pattern and the surface reflected light amount, which is a feature of the present invention, will be described.
As described above, as a result of the study by the present inventors, it is not the glossiness calculated based on the specularly reflected light from the original document that actually affects the color of the output image output by the color image forming apparatus. It was found that the surface reflection component from the toner at the observation angle at which the person views the output image is affected.

  The influence of the surface reflection component from the toner is as follows. In other words, when viewing an output image, a person looks at the document while avoiding the observation condition in which specular reflection light enters the eyes. This is because the reflected light is dazzling under regular reflection light conditions and the image content cannot be recognized properly. And the glossiness detected under specular reflection conditions and the amount of surface reflection at the angle when observing while avoiding normal specular reflection conditions are different, the glossiness value under specular reflection conditions and the color under normal observation conditions There is no exact correlation with the degree value.

As shown below, accurate color correction is difficult only by referring to the glossiness of the image.
FIG. 3 is a graph showing verification data performed by the present inventors. This verification data represents the relationship between the glossiness and the surface reflectance of an image output by changing the paper type and toner, respectively. The glossiness in the figure was measured at 60 ° using a gloss meter GM-26D manufactured by Murakami Color Research Laboratory. The surface reflectance was measured with a standard illuminant of D50 using X-Rite 938 (incident angle 0 ° / reflection angle 45 °), a spectrocolorimeter manufactured by X-Rite. First, the patch pattern to be measured in the output image is measured to obtain the first spectral reflectance. Next, a mirror surface state is created by laminating the patch pattern, and the second spectral reflectance is obtained by measuring again. When the surface of the toner is in a mirror state, all the surface reflection light in the light incident at 0 degree is reflected at 0 degree and does not diffuse on the toner surface. In other words, the 45 ° light receiving portion of the spectrocolorimeter X-Rite 938 does not receive the surface reflected light, and the spectral reflectance of an image in which the surface reflected light is 0 is measured. Therefore, by subtracting the first spectral reflectance that includes the surface reflected light and the second spectral reflectance that does not include the surface reflected light, the surface reflectance at 0 degree incidence / 45 degree reflection can be acquired. .

  Since the surface reflectance is spectral data having a value for each wavelength, the surface reflectance in FIG. 3 is plotted as an average value of the surface reflectance for each wavelength as the surface reflectance. Since the surface reflectance is light reflected from the toner surface without passing through the inside of the toner, it does not have spectral characteristics, and in the measurement with a normal spectrocolorimeter, the measured value is spectral reflection from the inside of the toner. Since the surface reflectance is uniformly added to the rate, there is no problem with the average value of the surface reflectance. In addition, said lamination process created the mirror surface state by sticking a colorless and transparent laminate seal with respect to a patch pattern to a patch.

  As shown in FIG. 3, there is a general tendency that the surface reflectance decreases as the glossiness increases to the middle glossiness, but there is no correlation at high glossiness. As a result, the surface reflectance and the glossiness are correlated. It turns out that there is no. As a result, depending on the paper type and toner, there are cases where the surface reflectance is large even if the glossiness is high, and even if there is no variation in the glossiness, the density may change due to variations in the surface reflectance. There is a high possibility that an image in which a value deviating from a map obtained by investigating the relationship between the glossiness and the unnecessary light component and the color (density) as described in Patent Document 1 and Patent Document 2 is formed.

  Further, when the surface reflectance is different by 1%, the color difference and the density difference may be 2.5 or more, and it is understood that accurate color correction cannot be performed only by referring to the glossiness. That is, in order to perform highly accurate color correction, it is necessary to perform color correction based on the surface reflectance under normal observation conditions, not the glossiness.

  Therefore, in the image forming apparatus of the present embodiment, the color of the color image of the test pattern and the amount of surface reflection are detected, and the image forming conditions are adjusted based on the detection result.

  Next, the color calibration image reading unit A serving as a detecting unit that detects the color of the color image of the test pattern and the surface reflected light amount, which is a feature of the present invention, is mounted in the image forming apparatus having the above configuration. The configuration and its operation will be described.

[Configuration of Image Reading Unit A]
FIG. 4 is a schematic configuration diagram illustrating an example of the overall configuration of the color calibration image reading unit A. A document to be detected (image reading target) can be placed on the support base 101. In this embodiment, the support base 101 of the scanner unit 2 is used.

  A light source 102 is provided on the support base 101, and the light emitted from the light source 102 is dispersed by a spectroscope 103, and the dispersed light passes through a polarizing filter (polarizing element) 104 and is irradiated with light. As shown in FIG. As the light source 102, a xenon lamp, a halogen lamp, an LED array, or the like can be used. In this embodiment, an LED array is used. The deflection filter can be operated in the direction indicated by the arrow M1 in FIG. Is possible. An illuminating unit as an illuminating unit that illuminates a detection target (reading target) image includes a light source 102, a spectroscope 103, and a polarizing filter (polarizing element) 104. The reflected light from the toner passes through the first polarizing filter 106 or the second polarizing filter 107 disposed in front of the light receiving unit 105 as a light receiving means for receiving the reflected light from the detection target (reading target), It is detected by the light receiving unit 105.

  In the present embodiment, the irradiation light is incident on the toner perpendicularly and the light receiving unit is installed at a position of 45 degrees with respect to the incident light. However, the angle observed with respect to the output image ( The angle position relationship between the illumination direction (light incident direction) by the illumination unit and the light reception direction by the light receiving unit 106 is as shown in FIG. It is not limited.

  The first polarizing filter 106 is disposed so as to be in the same direction as the polarization direction of the incident light, and the second polarizing filter 107 is disposed in a direction opposite to the polarization direction of the incident light. The first polarizing filter 106 and the second polarizing filter 107 are arranged so as to operate as indicated by an arrow M2 in FIG. That is, the state can be changed in three stages: a state where no deflection filter is inserted, a state where the first deflection filter 106 is inserted, and a state where the second deflection filter is inserted.

  For the light receiving unit 105, for example, a photodiode or the like is used. The illumination unit including the light source 102, the spectroscope 103, and the polarization filter (polarization element) 104, and the light receiving unit 105 are arranged in the carriage unit B. The carriage part B can move in the main scanning direction (direction in which a sheet as a recording member is conveyed in the image forming apparatus) as indicated by an arrow M3 in FIG.

  A white reference plate 108 is disposed at the end of the support base 101. The white reference plate 108 serves as a reference plate for adjusting variations in illumination light quantity and light reception sensitivity of the illumination unit and the light receiving unit 105. When performing color calibration, the white reference plate 108 is measured, and the variation between the illumination unit and the light receiving unit 105 is adjusted.

  FIG. 5 is a view of the carriage part B as viewed from below (bottom face). A plurality of the illuminating units and the light receiving units 105 are arranged in the sub-scanning direction (a direction orthogonal to the direction in which the sheet as the recording member is conveyed in the image forming apparatus) and are in an array. The carriage part B in which the illuminating part and the light receiving part 105 are arranged one-dimensionally moves in the main scanning direction, whereby it is possible to measure a patch of the entire test pattern.

  Note that the configuration shown in FIGS. 4 and 5 is not limited as long as the spectral reflectance and surface reflected light from the toner can be detected, and other configurations may be used.

[Color correction processing method]
Next, color correction processing using the detection result of the color calibration image reading unit A configured as described above will be described.
FIG. 6 is a block diagram illustrating an example of the flow of color correction processing in the image forming apparatus of the present embodiment. First, in order to perform color correction, a reference gradation patch as a reference test pattern is created in advance. This reference tone patch (test pattern) signal 200 is used as an input image. Next, image processing is performed based on a gradation correction conversion lookup table (hereinafter referred to as “conversion LUT”) 201, and an image in which toner is transferred onto a sheet through an electrophotographic process 202 is formed. In order to fix the toner on the paper, the toner is fixed on the paper in the fixing 203 and output as an output image 204. Next, the image reading unit A detects the chromaticity component and the surface reflection component of each reference gradation patch, and based on the detection result, the deviation of the target gradation is eliminated. Rewriting and correction of fixing conditions by the fixing unit 46 are performed.

FIG. 7 is a flowchart showing an example of the flow of color correction processing in the image forming apparatus of the present embodiment.
STEP 1: In order to start color calibration, a gradation correction chart (test chart), which is a test pattern serving as a reference by the user, is output. At the same time, in the image reading unit A, the deflection filters in the illumination unit and the light receiving unit are operated so that neither the illumination unit nor the light receiving unit is in the state in which the deflection filter is included, and the white reference plate 105 in FIG. Adjust the variation and the variation in light receiving sensitivity.

  STEP 2: Next, the output test chart is arranged in the image reading unit A, and each patch in the chart is detected. First, the spectral reflectance of the patch excluding the influence of the surface reflection component is measured. In order to eliminate the influence of the surface reflection component, the polarizing element of the illumination unit is, for example, P-polarized light, and the polarizing element on the light receiving side at that time is in a direction (S-polarized light) perpendicular to the polarizing element of the illumination unit. Each polarizing filter moves. Then, the spectral reflectance of each patch is acquired by the image reading unit A. Here, the measured spectral reflectance of the patch is Rps (λ). λ is a wavelength. The carriage part B moves in the sub-scanning direction, the patches on the test pattern are sequentially detected, and Rps (λ) is measured for each patch.

  STEP 3: Next, each patch in the chart is detected again. In STEP 3, data for calculating the surface reflection component is acquired. If the polarizing filter of the illumination unit is, for example, P-polarized light, each polarizing filter is moved so that the polarizing filter on the light receiving side becomes P-polarized light having the same polarization direction. In this state, the patch on the test pattern is read again. The spectral reflectance at this time is Rpp. Then, as in STEP 2, the carriage part B moves in the sub-scanning direction, the patches on the test pattern are sequentially detected, and Rpp (λ) is measured for each patch.

  STEP 4: Next, a surface reflection component is acquired using Rps (λ) and Rpp (λ) acquired in STEP 2 and STEP 3 above. The specific calculation of the surface reflection component is performed by the following method, for example. Rpp (λ) includes a surface reflection component and a P-polarized component in the reflected light from the inside of the toner, and Rps (λ) includes only an S-polarized component in the reflected light from the inside of the toner. Usually, the light intensity of P-polarized light and S-polarized light may be considered to be equal, and the light that has passed through the polarizing filter in the illumination unit is half that before passing. Therefore, assuming that the spectral reflectance S (λ) of the surface reflection component of the toner, S (λ) can be calculated by the following (Equation 1).

  S (λ) = 2 · (Rpp (λ) −Rps (λ)) (Equation 1)

  Since the surface reflected light component is reflected on the surface of the toner and has no spectral characteristics, and the reflectance at each wavelength is uniform, the reflectance for each wavelength of S (λ) is averaged in the visible wavelength range. The value is redefined as the surface reflectance S.

  STEP 5 & 5 ′: Next, for example, the target surface reflection light quantity determined in the design stage of the image forming apparatus and the spectral reflectance, or the fluctuation amount with respect to ID or L * a * b * converted from the spectral reflectance are calculated. Here, “ID” indicates the density of an image defined by ISO. “L * a * b *” is an index representing a color standardized by the CIE (International Commission on Illumination), and indicates a perceptual color difference perceived by humans. The measurement conditions for measuring the ID and L * a * b * are defined by ISO or CIE, but in this embodiment, for the sake of convenience, the measured spectrum is not limited to the definition of the measurement conditions. From the reflectance, ID and L * a * b * are calculated, and the fluctuation amount is obtained.

  STEP 6 & 6 ′: Next, the conversion LUT 201 is corrected to correct the above-described fluctuation, and the gamma correction is adjusted. Since Rps (λ) is a chromaticity value that does not depend on the influence of the surface state, that is, is not affected by variations in fixing, the value of Rps (λ) is used to correct the conversion LUT 201. That is, the variation in the toner adhesion amount is corrected. Further, Rps (λ) is halved by the polarization filter 104 of the illumination unit, and the P-polarized component of the reflected light from inside the toner excluding the surface reflected light is cut, so that the conversion LUT 201 Is corrected based on Rt (λ) calculated by the following (Equation 2).

  Rt (λ) = 4 · Rps (λ) (Formula 2)

  Here, color calibration is performed using the value “IDt” converted from the value of Rt (λ) to ID. For example, based on the difference in reflectance for each wavelength from the target spectral reflectance. Alternatively, a method of correcting the color variation amount may be used. On the other hand, since S (λ) shown in the above (Expression 1) represents reflection of only the surface reflection component regardless of the toner adhesion amount, the fixing condition is corrected using the value of S (λ).

Next, correction of the conversion LUT 201 will be described.
(1) in FIG. 8 shows the current γ characteristic of the printer. When the output (γOUT) of the printer γ conversion circuit is at a certain level, the image reading unit A reads IDt. The relationship between values (VSCN [current]) is shown.
FIG. 9 shows an example of a test pattern for detecting the current value of the printer γ characteristic. Seven levels of patches from the background to the solid are imaged at the center of the A4-size paper.

  The image reading unit A obtains “IDt” of each patch of the test pattern placed on the support base 101, thereby obtaining data plotted by circles in (1) of FIG. Based on this data, the gray level data for the output level can be known by using a method such as a cubic spline function or simply a linear approximation method.

  (3) in FIG. 8 is a target value of the printer γ characteristic. This shows the relationship between the level (γIN) input to the printer γ conversion circuit and the read value (VSCN [standard]) of the output pattern by the image reading unit A. Here, the reading value uses data by a reading device having a standard characteristic. (2) in FIG. 8 is a curve for correcting the machine difference of the γ characteristic of the image reading unit A. If the machine difference is small with respect to the target adjustment accuracy, this curve becomes a straight line indicating identity transformation.

  As described above, the printer γ correction curve shown in (4) of FIG. 8 can be obtained based on the characteristics (1) to (3) shown in FIG. By updating the γ conversion table (LUT) based on the printer γ correction data and setting it in the printer γ conversion circuit, the desired printer γ characteristics shown in (3) of FIG. 8 can be adjusted.

Next, correction of fixing conditions will be described.
For example, when “IDt” of the primary color solid patch is larger than the target surface reflection component, it can be said that the diffused light on the toner surface is large, that is, the unevenness is large. In that case, in order to reduce the unevenness, the fixing condition is corrected so that the surface reflection component approaches the target value by decreasing the fixing speed or increasing the fixing temperature and the fixing pressure.

  As described above, according to the first embodiment, the gradation is corrected based on the detection result of the surface reflection component affecting the color as well as the detection result of the color of the test pattern. In addition, it is possible to provide an image forming apparatus capable of outputting a stable image by correcting not only the high-precision color calibration but also the fixing conditions.

[Second Embodiment]
Next, color correction in the image forming apparatus according to the second embodiment of the present invention will be described.
FIG. 10 is a schematic configuration diagram illustrating an example of the overall configuration of the image reading unit of the image forming apparatus according to the present embodiment. The overall configuration of the image forming apparatus is the same as that of the first embodiment, and a description thereof will be omitted. In the first embodiment, it is necessary to scan the test pattern twice in order to detect the color detection and the surface reflection light. In the second embodiment, as shown in FIG. By arranging the second light receiving unit 110, color calibration can be performed by a single scan.

  In FIG. 10, a first polarizing filter 106 and a second polarizing filter 107 are arranged in front of the first light receiving unit 105 and the second light receiving unit 110 of the carriage unit C, respectively. The light source 102 and the spectroscope 103 are arranged at the center of the two light receiving units 105 and 110. The first polarizing filter 106 is arranged so that the polarization direction thereof is the same as the polarization direction of the polarizing filter 104 of the illumination unit. The second polarizing filter 107 is arranged so that the polarization direction is opposite to the polarization direction of the first polarizing filter 106. Since other configurations are the same as those of the first embodiment, description thereof will be omitted.

  FIG. 11 is an explanatory diagram illustrating the bottom surface of the image reading unit when the carriage unit C of FIG. 10 is viewed from below. The carriage portion C has a shape in which a line of light receiving sensor groups arranged in a line is added to the carriage portion B of FIG. 5 shown in the first embodiment.

FIG. 12 is a flowchart illustrating an example of the flow of color correction processing in the image forming apparatus according to the present embodiment.
STEP 1 is the same as in the first embodiment, but for the test pattern patch, STEP 3 for measuring the reflected light Rps (λ) from the toner excluding the surface reflected light, and for calculating the surface reflected light. STEP 2 for measuring Rpp (λ) necessary for the above is simultaneously performed.
By performing the above STEP 3 and STEP 2 simultaneously, it is possible to perform color correction processing with only one scan. Since the operation processing after STEP 4 is the same as that of the first embodiment, the description thereof is omitted.

  As described above, according to the second embodiment, there is no need to scan the test pattern twice in order to perform color detection and surface reflected light detection as in the first embodiment, and color calibration can be performed by one scan. Therefore, it is possible to shorten the execution time of color calibration, and it is possible to provide an image forming apparatus including a color calibration system with higher accuracy than before without waiting for the user.

[Third Embodiment]
FIG. 13 is a schematic configuration diagram showing an overall configuration of an image forming apparatus according to the third embodiment of the present invention. In the overall configuration of the image forming apparatus in FIG. 13, portions common to the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 13, in the third embodiment, an image reading unit including a color detection unit and a surface reflection component detection unit is installed on the downstream side of the fixing unit 46 in the sheet conveyance direction. The carriage part D constituting the image reading part of this embodiment is almost the same as the structure having the carriage part C of FIG. 10 described in the second embodiment. However, unlike the carriage unit C in FIG. 10, the image reading unit (carriage unit) D of the present embodiment does not operate for scanning and detecting patches of the test pattern, and the image reading unit (carriage unit). ) D is fixed downstream of the fixing unit 46 in the sheet conveying direction.

  Detection by the image reading unit (carriage unit) D is performed so that the test pattern patches are sequentially measured in accordance with the conveyance of the sheet. Since the methods of color detection, surface reflected light component detection, and color correction processing are the same as those in the first embodiment, description thereof will be omitted.

  In the third embodiment, for example, control may be added so that the image forming apparatus automatically outputs a test chart periodically to perform color calibration.

  According to the third embodiment, even if the user does not place a test pattern in the image reading unit A as in the first embodiment, the process is automatically performed inside the image forming apparatus and color correction is performed. Thus, color calibration can be easily performed with high accuracy.

[Fourth Embodiment]
In the first to third embodiments, the image forming apparatus including the image reading unit as the detection unit that reads the image of the test pattern independent of the scanner unit 2 in FIG. 2 has been described. In the image forming apparatus of the embodiment, it is possible to detect the color of the test pattern and detect the surface reflected light by using a scanner unit for forming a copy image of the document.

  FIG. 14 is a schematic configuration diagram showing an overall configuration of an image forming apparatus according to the fourth embodiment of the present invention. In the overall configuration of the image forming apparatus in FIG. 14, the same reference numerals are given to portions common to the first embodiment, and description thereof is omitted. When the user places a document to be copied and scans in the scanner section E of FIG. 14, a duplicate image is formed and output.

  FIG. 15 is a schematic configuration diagram illustrating an example of the overall configuration of the scanner unit of the image forming apparatus. When color calibration is performed in the image forming apparatus of the present embodiment, irradiation light is emitted from the light source 102 in FIG. For example, a halogen lamp or a white LED array is used as the light source 102. The light emitted from the light source 102 passes through the polarizing filter 104 operable in the direction of the arrow M4, and is irradiated onto the toner on the test pattern supported by the support base 101. The light reflected by the toner on the test pattern passes through the polarizing filter 106 operable in the direction of the arrow M5, is reflected by the mirror 301, forms a reduced image by the imaging lens 302, and is received by the light receiving unit 303. . The light receiving unit 303 uses a color CCD.

  On the other hand, when color calibration is not performed, that is, when a copy image of an original is formed, the polarization filters 104 and 106 are moved out of the optical path from illumination to light reception. As a result, it is possible to obtain reflected light from an unpolarized document. Since a technique for forming a copy image of a document can be the same as the conventional technique, the description thereof is omitted here. The illumination unit having the light source 102 and the polarization filter 104, the light receiving unit 303, and the like are arranged in the carriage unit F. The carriage unit F can be operated in the direction of the arrow M6, and reads a document while operating.

FIG. 16 is a flowchart illustrating an example of the flow of color correction processing in the image forming apparatus according to the present embodiment.
STEP 1: First, the reflected light of the white reference plate 108 is photographed in a state where the polarizing filter is disposed outside the optical path, and shading correction for variations in the light source 102 and white balance adjustment of the light receiving unit 303 are performed. . Next, the test pattern is output on a sheet, the sheet is placed on the support base 101, and the color correction process is started.

  STEP 2: The output test chart on the paper is placed in the image reading unit E, and the image reading unit E detects each patch in the test chart. First, the reflectance of the patch is measured without the influence of the surface reflection component. In order to eliminate the influence of the surface reflection component, the polarization element (polarization filter) 104 of the illumination unit is, for example, P-polarized light, and the polarization element (polarization filter) 106 on the reflected light side at this time is the polarization element (polarization filter) of the illumination unit. The polarization filters 104 and 106 are moved so that the polarization direction is orthogonal to the filter 104) (S-polarized light). Next, the image reading unit E acquires the signal value of the reflected light for each patch in the test chart. Here, regarding the measured brightness value of the reflected light of the patch, the brightness value of the red channel is Rps, the green channel is Gps, and the blue channel is Bps. The carriage unit F of the image reading unit E moves in the sub-scanning direction, sequentially detects patches on the test pattern, and measures Rps, Gps, and Bps for each patch.

  STEP 3: Next, each patch in the test chart is detected again. In STEP 3, data for calculating the surface reflection component is acquired. If the polarizing filter 104 of the illumination unit is, for example, P-polarized light, the polarizing filters 104 and 106 are moved so that the polarizing filter 106 on the reflected light side becomes P-polarized light having the same polarization direction. In this state, the patch on the test pattern is read again. Here, it is not necessary to read the luminance values of all the channels of the red channel, the green channel, and the blue channel, and only the green channel is read. The brightness value of the reflected light at this time is Gpp. Then, as in STEP 2, the carriage unit F moves in the sub-scanning direction, the patches on the test pattern are sequentially detected, and Gpp is measured for each patch.

  STEP 4: A surface reflection component is acquired using Gps and Gpp acquired in STEP 2 and STEP 3 above. If the surface reflection component in the green channel is Gs, Gpp (λ) includes the surface reflection component and the P-polarized component in the reflected light from the toner, and Gps includes only the S-polarized component in the reflected light from the toner. Gs can be calculated by the following (Formula 3).

  Gs = 2 · (Gpp−Gps) (Formula 3)

  Next, the surface reflectance S is obtained from Gs using the following (formula 4). Here, α and β are coefficients, and the relationship between Gs and S is obtained in advance by linear regression.

  S = α · Gs + β (Formula 4)

  STEP 5 & 5 ′: Next, for example, the target surface reflection light quantity determined in the design stage of the image forming apparatus and the variation amount with respect to ID (image density) converted from R, G, B values, L * a * b *, and the like. Calculate and adjust the conversion LUT and adjust the gamma correction to correct for variations. Also, the fixing conditions are adjusted. Since Rps, Gps, and Bps are chromaticity values that do not depend on the influence of the surface state, that is, are not affected by variations in fixing, the values of Rps, Gps, and Bps are used to correct the conversion LUT. That is, the variation in the adhesion amount is corrected. In Rps, Gps, and Bps, the amount of incident light is halved by the polarizing filter 104 of the illumination unit, and the P-polarized component of the reflected light from the inside of the toner excluding the surface reflected light is cut. When the correction is performed, the correction is performed based on R′ps, G′ps, and B′ps calculated by the following three formulas (Formula 5).

R′ps = 4 · Rps, G′ps = 4 · Gps, B′ps = 4 · Bps (Equation 5)

  Here, color calibration is performed using values “IDt” converted from ID values of R′ps, G′ps, and B′ps, respectively. On the other hand, since S represents reflection of only the surface reflection component regardless of the amount of adhesion, the fixing condition is corrected using the value of S. Subsequent STEPs are the same as those in the first embodiment, and will be omitted.

  According to the fourth embodiment, it is possible to perform both copying of a document and color calibration with a common scanner unit, without providing a scanner unit and an image reading unit for color calibration correction independently. Therefore, not only can the color calibration be performed with higher accuracy than before, but also the cost of the apparatus can be reduced.

As described above, according to each of the above embodiments, a color image of a predetermined test pattern is formed and output to a sheet as a recording member, and the color of the color image of the test pattern output to the sheet and the amount of reflected light on the surface are detected. To do. The image forming conditions of the image forming unit 3 are set so that the color detection result of the color image of the test pattern becomes a predetermined color and the detection result of the surface reflection light amount of the color image of the test pattern becomes a predetermined light amount. Can be adjusted. That is, (1) control for acquiring the amount of toner adhesion in the test pattern on the paper and correcting the toner adhesion based on the amount of variation, and (2) the amount of toner surface reflected light in the test pattern on the paper Both of the correction controls of the control for obtaining the amount of fluctuation of the light and correcting the amount of reflected light on the surface based on the amount of fluctuation are possible. Therefore, it is possible to perform color correction with high accuracy including the amount of surface reflection of the color image.
In each of the above embodiments, the image reading unit as the detection unit can detect the surface reflectance of the test pattern at various wavelengths by detecting the spectral reflectance of the image of the test pattern. This makes it possible not only to obtain necessary information for color correction, but also to convert chromaticity values such as XYZ, ID, and L * a * b * that are tristimulus values from the detection results. It becomes easy to divert the conventional color processing technology.
In the above-described embodiment, the image reading unit as the detection unit includes an illumination unit (light source 102, spectroscope 103) as an illumination unit that illuminates an image to be detected, and light reception that receives reflected light from the detection target. The illumination unit has a polarization element 104 capable of switching the polarization direction in the optical path of the illumination light, and the light reception unit 105 has the polarization direction in the optical path of the light reception. A polarizing element 106 that can be switched can be provided. In this case, the reflected light from the inside of the toner is detected by detecting the reflected light from the image to be detected while switching the polarization direction of the polarizing element 104 of the illumination unit and the polarization direction of the polarizing element 106 of the light receiving unit 105. The components can be separated and only the surface reflection component of the toner can be detected.
In the above-described embodiment, the image reading unit as the detection unit includes an illumination unit (light source 102, spectroscope 103) as an illumination unit that illuminates an image to be detected, and light reception that receives reflected light from the detection target. Two light-receiving units 105 and 110 as means, and the illumination unit has a polarization element 104 capable of switching the polarization direction in the optical path of the illumination light, and one light-receiving unit 105 is configured to receive the light. The optical path has a polarizing element 106 having the same polarization direction as that of the polarizing element 104 in the optical path of the illumination light, and the other light receiving unit 110 is in the optical path of the received light with respect to the polarizing element 104 in the optical path of the illumination light. Thus, the polarizing element 107 can be configured so that the polarization directions are orthogonal to each other. Also in this case, the reflected light from the inside of the toner is detected by detecting the reflected light from the image to be detected while switching the polarization direction of the polarizing element 104 of the illumination unit and the polarization direction of the polarizing element 106 of the light receiving unit 105. The components can be separated and only the surface reflection component of the toner can be detected. Further, in this case, the chromaticity value and the surface reflectance can be acquired by the carriage C of the image reading unit including the two light receiving units 105 and 110 only by one scanning (reading) movement, and color calibration is performed. It is possible to shorten the time for correction processing.
Further, in the above-described embodiment, the surface reflection light amount is calculated based on the light amount detected under the condition that the polarization direction of the polarization element 104 of the illumination unit and the polarization direction of the polarization element 106 of the light receiving unit are the same direction. It is calculated based on a value obtained by subtracting the amount of light detected under the condition that the polarization direction of 104 and the polarization direction of the polarization element 106 (107) of the light receiving unit are orthogonal to each other. With the calculated surface reflection light quantity, it is possible to obtain the spectral reflectance of only the toner surface reflection component that affects the appearance of human color. Further, since the surface reflectance is obtained from the spectral reflectance obtained under the same conditions as the geometric conditions for observing the color of the test pattern, it is different from normal human image viewing conditions such as 60 degree glossiness. Instead of the reflectance, it is possible to acquire the spectral reflectance of the surface reflected light that directly affects the appearance of the color.
In the above-described embodiment, the adjustment of the image forming condition includes the adjustment of γ correction for correcting the gradation, so that an appropriate adhesion amount can be obtained in each module such as charging, development, and transfer in the image forming apparatus. By controlling the amount of adhesion so as to be transferred onto the paper, it is possible to correct the color independent of variations in the amount of reflected light on the surface.
In the above-described embodiment, the image reading unit as the detection unit is arranged on the downstream side of the fixing unit 46 in the sheet conveyance direction, so that when the user performs color calibration, the output test pattern is displayed in the image reading unit. Even if it is not moved to, the test pattern can be automatically read in the image forming apparatus, and the work performed by the user can be reduced.
In the above embodiment, the fixing condition of the fixing unit 46 used in the conventional image forming apparatus is adjusted by adjusting the fixing condition of the fixing unit 46 based on the surface reflected light amount detected by the image reading unit as the detecting unit. It is possible to suppress fluctuations in the amount of reflected light from the surface simply by adjusting the fixing conditions while maintaining the configuration. In addition, since it is possible to correct the variation in the surface reflectance that greatly affects the color, which has not been taken into account in the conventional apparatus, it is possible to perform color correction that is more stable than in the past.
Further, in the above-described embodiment, the scanner unit and the color calibration are performed by using the scanner unit 2 as an image reading unit that reads an image of a document to be copied as the image reading unit for color calibration correction as the detection unit. Even if the image reading unit for image correction is not provided independently, both the copying of the original and the color calibration can be performed by the common scanner unit 2. Therefore, not only can the color calibration be performed with higher accuracy than before, but also the cost of the apparatus can be reduced.
Further, in the above embodiment, the image processing unit 44 that can also be used as test pattern data generating means for generating predetermined test pattern data is provided, and the image forming unit 3 applies the test pattern data generated by the image processing unit 44 to the test pattern data. Based on this, a color image of a test pattern may be formed and output to a sheet. In this case, it is not necessary to prepare a test chart document for color calibration.
In the above-described embodiment, the image forming unit 3 may be configured to form a color image of the test pattern based on the test pattern data obtained by reading the original of the test pattern by the scanner unit 2 and output the test pattern on the paper. . In this case, it is not necessary to previously register a program or data for generating test pattern data in the image processing unit 44 or the like, and an original with an arbitrary test pattern is set in the scanner unit 2 and color calibration is performed. be able to.

A image reading unit B carriage unit 2 scanner unit 3 image forming unit 40 control unit 44 image processing unit

JP-A-10-322490 JP-A-7-147622

Claims (11)

An image reading unit that reads an image, a color image forming unit that forms a color image on the basis of image data read by the image reading unit and outputs the color image to a recording member, and adjusts image forming conditions of the color image forming unit An image forming apparatus comprising image forming condition adjusting means,
The color image forming means is configured to be capable of forming a color image of a predetermined test pattern and outputting it to a recording member,
A detecting means for detecting the color of the color image of the test pattern output to the recording member by the color image forming means and the amount of surface reflection;
The image forming condition adjusting unit adjusts the image forming condition of the color image forming unit based on the color of the color image of the test pattern detected by the detecting unit and the surface reflected light amount. . The image forming apparatus according to claim 1.
The image forming apparatus, wherein the detection unit detects a spectral reflectance of an image of the test pattern. The image forming apparatus according to claim 1 or 2,
The detection means includes an illumination means for illuminating an image to be detected, and a light receiving means for receiving reflected light from the detection target.
The illumination means has a polarization element capable of switching the polarization direction in the optical path of the illumination light,
The image forming apparatus according to claim 1, wherein the light receiving unit includes a polarization element capable of switching a polarization direction in an optical path of the light reception. The image forming apparatus according to claim 1 or 2,
The detection means includes an illuminating means for illuminating an image to be detected, and two light receiving means for receiving reflected light from the detection target,
The illumination means has a polarization element in the optical path of the illumination light,
Of the two light receiving means, one light receiving means has a polarizing element having a polarization direction in the same direction as that of the polarizing element in the light path of the illumination light in the light receiving optical path, An image forming apparatus comprising: a polarizing element having a polarization direction orthogonal to a polarizing element of the optical path of the illumination light in a light receiving optical path. The image forming apparatus according to claim 3 or 4,
The surface reflection light amount is determined based on the light amount detected under the condition that the polarization direction of the polarization element of the illumination unit and the polarization direction of the light reception unit are the same, and the polarization direction of the polarization element of the illumination unit and the light reception. An image forming apparatus characterized in that the value is calculated based on a value obtained by subtracting the amount of light detected under a condition in which the polarization direction of the polarizing element of the means is orthogonal. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the adjustment of the image forming condition by the image forming condition adjusting unit includes adjustment of γ correction for correcting gradation. The image forming apparatus according to claim 1,
The color image forming unit includes a fixing device that fixes an image formed on the recording member,
The image forming apparatus according to claim 1, wherein the detection unit is disposed on the downstream side of the fixing device in the recording member conveyance direction. The image forming apparatus according to claim 1,
The color image forming unit includes a fixing device that fixes an image formed on the recording member,
The image forming condition adjusting unit adjusts a fixing condition of the fixing device based on a surface reflected light amount detected by the detecting unit. The image forming apparatus according to claim 1,
An image forming apparatus characterized in that the image reading unit is also used as the detection unit. The image forming apparatus according to claim 1,
A test pattern data generating means for generating predetermined test pattern data;
The color image forming unit forms a color image of the test pattern based on the test pattern data generated by the test pattern data generation unit and outputs the color image to a recording member. The image forming apparatus according to claim 1,
The color image forming unit forms a color image of the test pattern based on test pattern data obtained by reading the original image of the test pattern by the image reading unit and outputs the color image to a recording member.