JP4940780B2 - Composite image and image forming apparatus - Google Patents

Description

  The present invention includes a tandem type color printer, a color copying machine, and a color complex machine having a photosensitive drum and an intermediate transfer belt, which perform image color misregistration and image density correction processing when the power is turned on, for example. The present invention relates to an applicable composite image and an image forming apparatus.

  In recent years, a tandem type color printer, a color copying machine, and a color complex machine thereof are often used. In these image forming apparatuses, an image is formed using toner agents for yellow (Y), magenta (M), cyan (C), and black (K) colors. These image forming apparatuses include a laser writing unit, a developing unit, and a photosensitive drum for each color, and an intermediate transfer belt and a fixing device for superimposing the respective colors and outputting them to a sheet.

  For example, a Y-color laser writing unit draws an electrostatic latent image on a Y-color photosensitive drum based on image information. In the laser writing unit and the developing unit, a toner agent for Y color is attached to the electrostatic latent image drawn on the photosensitive drum to form a toner image. The photosensitive drum transfers the Y color toner image to the intermediate transfer belt. Similar processing is performed for the other M, C, and K colors, and transfer to the intermediate transfer belt is performed. At that time, the toner images of the respective colors are accurately superimposed on the intermediate transfer belt. The toner image transferred to the intermediate transfer belt in this way is transferred to the output paper and then fixed by the fixing device.

  According to this image forming apparatus, yellow (Y), magenta (M), cyan (C), and black (K) toners that reproduce color images on output paper in order to maintain optimum color image formation quality. It is essential to correct the image output color shift and image density shift regularly or irregularly.

  With respect to these correction processes, a color misregistration correction pattern and an image density correction pattern formed on the intermediate transfer belt or the conveyance material transfer belt are detected by a detection unit such as an image detection sensor, and are used as a reference for each color toner agent. The correction amount of the color shift and the image density shift with respect to the target value is calculated, and the image is corrected by controlling the developing bias, the laser drive circuit, and the like using the correction amount.

  Regarding this type of image forming apparatus, Patent Document 1 discloses a color image forming apparatus. According to this color image forming apparatus, the toner mark for image control formed on the moving body (intermediate transfer belt) from each toner image forming unit is sequentially detected by the position (color shift) detecting means and the density detecting means. Both the relative position shift (color shift) amount of each single color toner image and the density error with respect to the image information are detected while sharing the same image control mark.

  As described above, when the color image forming apparatus is configured, it is possible to shorten the initial time until the actual recording image is formed, and the toner agent consumption amount and waste toner in each toner image forming unit. The amount of emissions can be reduced.

JP 2004-333837 PR (page 14 Fig. 4)

  By the way, according to the conventional image forming apparatus, since the color misregistration correction pattern and the image density correction pattern are separately formed / detected to perform the correction processing, a series of correction processing takes time. In addition, according to the color image forming apparatus according to Patent Document 1, since the position shift (color shift) amount and the density error are detected using the same image control mark, the image control formed for the low density correction is performed. The mark for use is also used for position (color misregistration) correction. However, if an edge of an image control mark formed at a low density is to be detected by a reflective sensor, the edge is blurred and the detection signal has a long up / down time. As a result, the detection accuracy of position (color misregistration) correction may deteriorate.

  SUMMARY OF THE INVENTION Therefore, the present invention solves the above-described problems, and provides a composite printed image and an image forming apparatus that can accurately detect edges while reducing the time required for a series of correction processes. With the goal.

According to the first aspect of the present invention, in the composite image formed on the image carrier during the color misregistration correction and image density correction processing of the image forming apparatus, the direction parallel to the rotation axis of the image carrier is the main scanning direction. When the direction in which the image carrier rotates is the sub-scanning direction, the image carrier is formed of two sides that have a predetermined width and come into contact with each other at a predetermined angle, and the first side is the main side. It is formed by a straight line portion that is parallel to the scanning direction, and the second side is formed by an inclined portion that is inclined with respect to either the main scanning direction or the sub-scanning direction, and corresponds to the color misregistration correction processing of the image forming apparatus. a first indicia image that will be detected Te, the side of the interior angle of the inclined portion linear portion forming the two sides in the first mark image, a predetermined region having a distance for identification with the first indicia image, is formed at the same concentration as the first indicia image, the image of the image forming apparatus It is characterized in further comprising a second indicia image that will be detected in accordance with the degree correction process.

Synthesis indicia image as claimed in claim 2, wherein the Oite to claim 1, the first and second indicia images, simultaneously formed on the image bearing member at the time of the color misalignment correction process of the image forming apparatus and the time of image density correction processing, and it is characterized in Rukoto simultaneously detected.

The image forming apparatus according to claim 3 , wherein a mark image of each color corresponding to the image information is formed, and a multicolor mark image is formed on the image carrier by superimposing the mark images of the respective colors. In the apparatus, an image forming means for forming a composite mark image including a first mark image and a second mark image on the image carrier, and a composite mark image formed on the image carrier by the image forming means are detected. Control for extracting the information of the first mark image and correcting the color misregistration from the detected mark image detected by the detection means and the synthesized mark image and for correcting the image density by extracting the information of the second mark image The first mark image has a predetermined width when the direction parallel to the rotation axis of the image carrier is the main scanning direction and the direction in which the image carrier rotates is the sub-scanning direction. And formed with two sides that come into contact with each other at a predetermined angle. Of the image forming apparatus, and the second side is formed of an inclined portion that is inclined with respect to the main scanning direction or the sub-scanning direction. The second mark image is detected in accordance with the color misregistration correction process. The second mark image has an identification distance from the first mark image on the inner angle side of the straight line portion and the inclined portion that form two sides of the first mark image. in a predetermined area having, formed at the same concentration as the first indicia image is detected according to the image density correction processing in the image forming apparatus is characterized in Rukoto.

According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the third aspect, wherein a series of correction processing by the image forming unit, the detecting unit, and the control unit is performed when the image forming apparatus is turned on and / or during the waiting time of the image forming apparatus. It is characterized in that it is executed when the power saving mode for reducing the power consumption is canceled and / or when regular or irregular maintenance is completed in the image forming apparatus.

According to the composite mark image according to claim 1, the first mark image formed by the two sides and the predetermined area having a distance for identification with the first mark image formed at the same density as the first mark image. 2 mark images. With this configuration, the first mark image and the second mark image can be formed / detected separately, so that the edges for color misregistration correction can be accurately formed even if the first and second mark images have the same density. It can be detected.

According to the image forming apparatus of the third aspect , the control unit for correction is provided. For example, from the composite printed image formed / detected on the image carrier during the series of correction processing performed when the power is turned on, the first The color image is corrected by extracting the information of the mark image, and the image density is corrected by extracting the information of the second mark image. .

  With this configuration, it is possible to simultaneously form / detect a color misregistration correction print image and an image density correction print image, thereby reducing the time required for a series of correction processes. Further, since the first mark image can be used for color misregistration correction and the second mark image can be used for image density correction, in the composite mark image in which the density of the second mark image is lowered for low density correction. However, the first mark image can be formed with sufficient density, and the edge for color misregistration correction can be detected with high accuracy.

  Hereinafter, a composite printed image and an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing a configuration example of a color image forming apparatus 100 as an embodiment of the present invention. A color image forming apparatus 100 shown in FIG. 1 constitutes an example of a tandem type image forming apparatus. In a color printer, a color copying machine, and a color complex machine thereof, a multicolor printed image corresponding to image information is imaged. It is used as a device that is formed on a carrier and transferred onto a sheet.

  The color image forming apparatus 100 includes an intermediate transfer belt 6, an image forming unit 10Y, 10M, 10C, 10K, a secondary transfer roller 7A, a cleaning unit 8A, an image detection sensor 12, a control unit 15, and a fixing device 19. The

  The intermediate transfer belt 6 constitutes an example of an image carrier and is formed in an endless shape. The yellow (Y), magenta (M), cyan (C), and black (K) toner images corresponding to the image information are superimposed on the intermediate transfer belt 6 and transferred onto the paper. Around the intermediate transfer belt 6, image forming units 10Y, 10M, 10C, and 10K constituting an example of an image forming unit that forms a YMCK mark image are provided. On the intermediate transfer belt 6, toner that is a mark image is provided. An image is formed.

  The image forming unit 10Y includes a photosensitive drum 1Y, a charger 2Y, a laser writing unit 3Y, a developing unit 4Y, a primary transfer roller 7Y, and an image forming body cleaning unit 8Y. A yellow (Y) toner image is formed.

  The photoreceptor drum 1Y is rotatably provided at a position close to the intermediate transfer belt 6 so as to form a Y color toner image. For example, an organic photoconductor (OPC) drum is used as the photoconductor drum 1Y.

  A charger 2Y is provided at a position close to the photosensitive drum 1Y, and the surface of the photosensitive drum 1Y is charged to a predetermined potential. For example, a scorotron band electrode is used for the charger 2Y, and a DC voltage of several hundreds [V] is applied.

  A laser writing unit 3Y is provided in the vicinity of the photosensitive drum 1Y. A laser beam for Y color having a predetermined intensity based on image information is applied to the photosensitive drum 1Y charged by the charger 2Y. It is made to scan. The main scanning direction in this scanning is a direction parallel to the rotation axis of the photosensitive drum 1Y. The photosensitive drum 1Y rotates in the sub-scanning direction, and the laser writing unit 3Y performs deflection scanning in the main scanning direction on the photosensitive drum 1Y rotating in the sub-scanning direction. Is formed.

  A developing unit 4Y is provided at a position close to the photosensitive drum 1Y, and operates to develop a Y-color electrostatic latent image formed on the photosensitive drum 1Y to form a toner image. The Y-color toner image formed on the photosensitive drum 1Y is transferred onto the intermediate transfer belt 6 by a primary transfer roller 7Y to which a primary transfer bias voltage having a polarity opposite to that of the toner agent is applied (1). Next transfer).

  A cleaning unit 8Y is provided in the vicinity of the photosensitive drum 1Y to remove the toner agent remaining on the photosensitive drum 1Y after the primary transfer. The image forming unit 10Y is configured as described above.

  In this example, an image forming unit 10M is provided at the next stage of the image forming unit 10Y. The image forming unit 10M includes a photosensitive drum 1M, a charger 2M, a laser writing unit 3M, a developing unit 4M, a primary transfer roller 7M, and an image forming body cleaning unit 8M. A magenta (M) toner image is formed.

  An image forming unit 10C is provided at the next stage of the image forming unit 10M. The image forming unit 10C includes a photosensitive drum 1C, a charger 2C, a laser writing unit 3C, a developing unit 4C, a primary transfer roller 7C, and an image forming member cleaning unit 8C. A cyan (C) toner image is formed.

  An image forming unit 10K is provided at the next stage of the image forming unit 10C. The image forming unit 10K includes a photosensitive drum 1K, a charger 2K, a laser writing unit 3K, a developing unit 4K, a primary transfer roller 7K, and an image forming member cleaning unit 8K. A black (K) toner image is formed.

  For the configurations and functions of the image forming units 10M to 10K, refer to the image forming unit 10Y.

  The toner image temporarily transferred onto the intermediate transfer belt 6 by the image forming units 10Y to 10K is conveyed toward the secondary transfer roller 7A. The secondary transfer roller 7A transfers the color toner image formed on the intermediate transfer belt 6 onto a sheet conveyed from a sheet feeding unit (not shown) (secondary transfer). The transferred paper is subjected to fixing processing by the fixing device 19. In this way, the sheet on which the color image corresponding to the image information is transferred is output by a conveying unit (not shown).

  A cleaning unit 8A is provided at the subsequent stage of the secondary transfer roller 7A to clean the toner agent remaining on the intermediate transfer belt 6 that has become unnecessary after the secondary transfer. The cleaning unit 8 </ b> A has a charge removing unit that removes charges from the intermediate transfer belt 6 and a pad that removes the toner agent remaining on the intermediate transfer belt 6, and resets the printed image on the intermediate transfer belt 6.

  An image detection sensor 12 that constitutes an example of a detection unit is provided in an upper region of the cleaning unit 8A in which the upper surface of the intermediate transfer belt 6 can be seen, and the intermediate transfer belt 6 is provided during correction processing in the color image forming apparatus 100. The formed composite correction pattern (composite print image) is detected. Based on the composite correction pattern data detected by the image detection sensor 12, the color misregistration correction process and the image density correction process are performed in the control unit 15 constituting an example of the control unit. The color image forming apparatus 100 is configured as described above.

  2A and 2B are diagrams illustrating a configuration example of the composite correction pattern P detected by the image detection sensor 12 during the correction process. A composite correction pattern P shown in FIG. 2A constitutes an example of a composite printed image, and includes a color misregistration correction pattern P1 and an image density correction pattern P2, and is applied onto the intermediate transfer belt 6 by the image forming units 10Y to 10K during correction processing. It is formed.

  The color misregistration correction pattern P1 has a predetermined width and has two sides that are in contact with each other at a predetermined angle, for example, a straight line portion P1a that is parallel to the main scanning direction, and a main or sub scanning direction. On the other hand, it is formed with an inclined portion P1b that is inclined, and is used as a color misregistration correction pattern during correction processing.

  The image density correction pattern P2 is formed at the inner corners of the two sides of the color misregistration correction pattern P1 with a density different from that of the color misregistration correction pattern P1, and is used as an image density correction pattern at the time of correction processing. However, the position to be formed is not limited to the inner angles of the two sides, and may be, for example, an outer angle in contact with the inclined portion P1b. The composite correction pattern P has a size of about 8 mm square (x = 8 mm, y = 8 mm), for example, and is formed on the intermediate transfer belt 6.

  FIG. 2B shows a configuration example of the composite correction pattern P formed on the intermediate transfer belt 6 while changing the state. In this example, the composite correction pattern P is formed by changing the density of the image density correction pattern P2 in five steps for each toner agent of Y, M, C, and K colors. The first density is the lowest density and the fifth density is the highest density. The first density is the Y, M, C, K pattern, and the second density is the Y, M, C, K pattern. Are finally formed, and finally, the fifth density Y, M, C, and K color patterns are formed, and a total of 20 composite correction patterns P are formed.

  However, in the 20 composite correction patterns P, the color misregistration correction pattern P1 is formed with a constant density higher than the image density correction pattern P2. However, the present invention is not limited to this, and in order to reduce the amount of toner agent used, the image detection sensor 12 may be formed with a minimum density that can sufficiently detect an edge.

  In this example, all the composite correction patterns P are arranged in one row so that they can be detected by one image detection sensor 12. However, for example, they are arranged in two rows and detected by two image detection sensors 12. It may be.

  3A and 3B are diagrams showing an example of the composition correction pattern P ′. Similar to the composite correction pattern P, the composite correction pattern P ′ shown in FIG. 3A constitutes an example of a composite mark image, and includes a color misregistration correction pattern P1 ′ and an image density correction pattern P2 ′.

  The color misregistration correction pattern P1 ′ has a predetermined width and has two sides that contact each other at a predetermined angle, for example, a straight line portion P1a ′ that is parallel to the main scanning direction, It is formed of an inclined portion P1b ′ that is inclined with respect to the sub-scanning direction.

  The image density correction pattern P2 'is formed with the same or very similar density as the color misregistration correction pattern P1', with an identification distance d at the inner corners of the two sides of the color misregistration correction pattern P1 '. The combined correction pattern P ′ is formed when the color misregistration correction pattern P <b> 1 ′ and the image density correction pattern P <b> 2 ′ are the same or very close in density and the edge cannot be determined.

  FIG. 3B shows a configuration example of the composite correction pattern P ′ formed on the intermediate transfer belt 6. In this example, a total of four toners are formed at the highest sixth density, one for each Y, M, C, and K toner. In this example, the composite correction pattern P ′ is formed at the subsequent stage of the composite correction pattern P shown in FIG. 2B. Accordingly, the density correction patterns P2 and P2 'are arranged so that the densities thereof are sequentially increased.

  FIG. 4 is a block diagram illustrating a configuration example of a correction processing system of the color image forming apparatus 100. The color image forming apparatus 100 shown in FIG. 4 is obtained by extracting only the blocks of the correction processing system from the one shown in FIG. 4, the color image forming apparatus 100 includes an image forming unit 10 including an intermediate transfer belt 6, an image detection sensor 12, a control unit 15, and image forming units 10Y, 10M, 10C, and 10K.

  In the correction process, first, the image forming unit 10 forms the combined correction patterns P and P ′ shown in FIGS. 2 and 3 on the intermediate transfer belt 6. In FIG. 4, the Y-color composite correction patterns P and P ′ are collectively indicated as P (Y). Hereinafter, similarly, the M color, the C color, and the K color are denoted as P (M), P (C), and P (K).

  An image detection sensor 12 is provided in a region where the upper surface of the intermediate transfer belt 6 can be seen, and detects the combined correction patterns P and P ′ formed on the intermediate transfer belt 6 and outputs a detection signal S2. As the image detection sensor 12, a reflective optical sensor, an image sensor, or the like is used. These sensors include a light emitting element and a light receiving element, and light is emitted from the light emitting element to the combined correction patterns P and P ′, and the reflected light is detected by the light receiving element. That is, the detection signal S2 output from the image detection sensor 12 is an analog signal including information on the color shift component and the image density component corresponding to the detected reflected light.

  The control unit 15 is connected to the image detection sensor 12, and the detection signal S2 output from the image detection sensor 12 is input. The control unit 15 includes a signal processing unit 16, a CPU 17, and a RAM 18.

  The signal processing unit 16 receives the detection signal S2 detected by the image detection sensor 12, performs sampling based on the clock signal Dclk formed inside or outside, and outputs sampling data Ds. The sampling data Ds is composed of digital data including information on color misregistration components and image density components.

  The output sampling data Ds is input to the CPU 17 and RAM 18 connected to the signal processing unit 16, stored in the RAM 18, and used for correction processing in the CPU 17. The CPU 17 extracts data necessary for the correction process from all the sampling data Ds stored in the RAM 18, compares the calculation result of the extracted data with the target value set inside, and corrects the color misregistration correction data Dr3. The image density correction data Dr4 is calculated / output. The output color misregistration correction data Dr3 and image density correction data Dr4 are input to the image forming unit 10.

  In FIG. 4, an image forming unit 10 includes a laser writing unit 3 having laser writing units 3Y, 3M, 3C, and 3K, a developing unit 4 including developing units 4Y, 4M, 4C, and 4K, and photosensitive drums 1Y, 1M, 1C, 1K. The color misregistration correction data Dr3 input to the image forming unit 10 is mainly input to the laser writing unit 3 and used for color misregistration correction. The laser writing unit 3 corrects the irradiation position of the laser beam applied to the photosensitive drums 1Y to 1K based on the input color misregistration correction data Dr3.

  The image density correction data Dr4 is mainly input to the developing unit 4 and used for image density correction. The developing unit 4 corrects the toner agent adhesion amount based on the input image density correction data Dr4. In this way, color misregistration and image density correction processing is performed.

  Further, the combined correction patterns P and P ′ formed on the intermediate transfer belt 6 during such correction processing are detected by the image detection sensor 12 and then transferred to the paper by the cleaning unit 8A (not shown). It is removed from the intermediate transfer belt 6.

  These series of correction processes are executed when the color image forming apparatus 100 is turned on, when the color image forming apparatus 100 is released from the power saving mode, when the maintenance of the color image forming apparatus 100 is completed, or the like. . By performing the correction process at such timing, the image forming process can be executed in an optimum state in which the color misregistration and the image density are adjusted after the fixing temperature reaches the specified temperature.

  5A to 5H are diagrams illustrating sampling examples of the detection signal S2 in the signal processing unit 16. FIG. The composite correction pattern P shown in FIG. 5A is detected by the image detection sensor 12 and is output as a detection signal S2.

  FIG. 5B is a diagram illustrating a waveform example of the output detection signal S2. In FIG. 5B, the horizontal axis represents time t, and the vertical axis represents the amplitude level. In the figure, L1 is an amplitude level indicating the density of the color misregistration correction pattern P1. In the figure, L2 is an amplitude level indicating the density of the image density correction pattern P2. In the figure, L3 is an amplitude level indicating the reflectivity of the intermediate transfer belt. Further, the threshold value Lth is an amplitude level set for detecting the edge of the detection signal S2.

FIG. 5C is a diagram illustrating a waveform example of the trigger signal VTOP (image leading edge detection signal) input to the signal processing unit 16 when the detection signal S2 is sampled. The signal processing unit 16 calculates time data using the rising time of the trigger signal VTOP as the reference time t0. For example, the time data T1 at time ta is defined by the elapsed time from time t0,
T1 = ta−t0 Equation 1
Is calculated by

  FIG. 5D is a diagram illustrating a waveform example of the clock signal Dclk used for sampling. The signal processing unit 16 sequentially reads the amplitude level of the detection signal S2 at the rising time of the input clock signal Dclk, and outputs the sampling data Ds. In the sampling data Ds, the time data Ts and the amplitude data Ls are written and set to Ds (Ts, Ls).

  5E to 5H are diagrams illustrating examples of detecting the sampling data Ds output by the signal processing unit 16. For example, FIG. 5E shows an example of detection of sampling data Ds at time ta, which is formed from time data T1 and amplitude data L3, and becomes Ds (T1, L3). Similarly, sampling data Ds (T2, L4), Ds (T3, Lth), and Ds (T4, L1) at times tb to td are sequentially formed. These samplings are performed for all of the detection signals S2, and the signal processing unit 16 outputs a large number of sampling data Ds.

  FIG. 6 is a diagram illustrating an example (part 1) of data extraction by the control unit 15. FIG. 6A is a top view illustrating an example of detection of the first density composite correction pattern P. FIG. FIG. 6B is a diagram illustrating a waveform example of the detection signal S2 related to the composite correction pattern P of the first density. In FIG. 6B, the horizontal axis is time t. The vertical axis represents the amplitude level of the detection signal S2.

  The detection signal S2 illustrated in FIG. 6B is input to the control unit 15, and converted / outputted into the sampling data Ds by the signal processing unit 16 as described above. The output sampling data Ds is stored in the RAM 18. The sampling data Ds stored in the RAM 18 is extracted by the CPU 17 for data necessary for correction processing.

  Prior to this data extraction, a threshold value Lth is set. The threshold value Lth is set for detecting an edge of the color misregistration correction pattern P1, and is set to an amplitude level between the amplitude data L1 and L2. Since the threshold value Lth is preferably a constant value in all data extraction, in this example, the threshold value Lth may be a value between the amplitude data L1 and L2 of the fifth density at which the two values are closest.

  The CPU 17 extracts sampling data Ds (hereinafter referred to as edge detection data De) in which the set threshold value Lth matches the amplitude data Ls. For example, for the first concentration, De1 to De16 are extracted. Similarly, when the fifth concentration is extracted, De1 to De80 are extracted. The CPU 17 further extracts data necessary for calculating the color misregistration correction data Dr3 and the image density correction data Dr4 based on the edge detection data De.

  First, in order to extract data necessary for calculating the color misregistration correction data Dr3, the edge detection time Te and Te1 to Te16 are extracted for the first density from the edge detection data De. The edge detection time Te represents the edge of the color misregistration correction pattern P1, and is used for calculating the color misregistration correction data Dr3.

Next, in order to extract data necessary for calculating the image density correction data Dr4, first, the edge detection data De of the image density correction pattern P2 is extracted. In this example, there are four edge detection data De for one composite correction pattern P, and the second and third are data obtained by detecting the edge of the image density correction pattern P2. For example, if the first density is yellow, the edge detection data De2 and De3 are obtained. This can be expressed as an expression:
The second edge detection data De is
De {4 × (N−1) +2} Equation 2
The third edge detection data De is
De {4 × (N−1) +3} Equation 3
It becomes. N represents the number of composite correction patterns P. In this example, since 20 composite correction patterns P are formed in total (4 color toner agents × 5 density), [N = 1 to an integer of 1 to 20].

  Next, the edge detection time Te of the edge detection data De of Expression 2 and Expression 3 is extracted, and the sampling data Ds having the time data Ts between them is read (extracted) from the RAM 18. For example, in the first density yellow, all sampling data Ds (Y1) between the edge detection times Te2 to Te3 of De2 to De3 is read from the RAM 18. Since the amplitude data Ls of the read sampling data Ds (Y1) indicates the density of the image density correction pattern P2, it is used to calculate the image density correction data Dr4. In this way, the control unit 15 extracts data necessary for calculating the color misregistration correction data Dr3 and the image density correction data Dr4 based on the detection signal S2 that has detected the composite correction pattern P.

  As in this example, when the image density correction pattern P2 is arranged at the inner angle of the color misregistration correction pattern P1 composed of two sides, the edge detection data De of both the correction patterns P1 and P2 are compared with one threshold value Lth. Can be extracted. Further, the edge detection of the image density correction pattern P2 formed with a low density can be performed with high accuracy.

  FIG. 7 is a diagram illustrating a data extraction example (part 2) of the control unit 15. FIG. 7A is a top view illustrating a detection example of the composite correction pattern P ′. The composite correction pattern P ′ shown in FIG. 7A is formed subsequent to the composite correction pattern P (first density) and other composite correction patterns P (second to fifth density) in FIG. 6A.

  FIG. 7B is a diagram illustrating a waveform example of the detection signal S2 related to the composite correction pattern P ′. The detection signal S2 shown in FIG. 7B is connected to the detection signal S2 shown in FIG. 6B and is detected by the image detection sensor 12 at the same time. However, since the waveform shapes are different, it is necessary to extract data by a method different from the synthetic correction pattern P.

  The detection signal S2 in FIG. 7B is input to the control unit 15 and converted / outputted into the sampling data Ds by the signal processing unit 16 as described above. The output sampling data Ds is stored in the RAM 18. The CPU 17 extracts data necessary for the correction process from the sampling data Ds stored in the RAM 18. Also in this data extraction, first, the amplitude data Ls of the sampling data Ds is compared with the threshold value Lth, and the edge detection data De81 to De104 in which the threshold value Lth and the amplitude data Ls match are extracted. This threshold value Lth is preferably set to the same amplitude level as that used for edge detection of the composite correction pattern P.

The CPU 17 further extracts data necessary for calculating the color misregistration correction data Dr3 and the image density correction data Dr4 based on the extracted edge detection data De81 to De104. Prior to extraction of data necessary for each correction, edge detection data De of the image density correction pattern P2 ′ is extracted. For one composite correction pattern P ′, there are six edge detection data De, and the third and fourth are data indicating the edge of the image density correction pattern P2 ′. For example, in the case of yellow, the edge detection data De83 and De84 are obtained. This can be expressed as an expression:
The third edge detection data De is
De {6 × (M−1) +83} Equation 4
The fourth edge detection data De is
De {6 × (M−1) +84} Equation 5
It becomes. M represents the number of composite correction patterns P ′. In this example, a total of four composite correction patterns P ′ (four color toner agents × 1 density) are formed, and therefore [M = 1 to an integer of 1 to 4].

  In order to extract data necessary for calculating the color misregistration correction data Dr3, the edge detection data De shown in the equations 4 and 5 is removed from all the extracted edge detection data De. The edge detection time Te is extracted from the edge detection data De after the removal. This edge detection time Te represents the edge of the color misregistration correction pattern P1 'and is used for calculating the color misregistration correction data Dr3.

  Next, in order to extract data necessary for the calculation of the image density correction data Dr4, the edge detection time Te of the edge detection data De of the expressions 4 and 5 is extracted, and the sampling data Ds having the time data Ts therebetween. (Multiple) are extracted from the RAM 18. The amplitude data Ls (plural) of the extracted sampling data Ds represents the density of the image density correction pattern P2 ', and is used for calculating the image density correction data Dr4. In this way, the control unit 15 extracts data necessary for calculating the color misregistration correction data Dr3 and the image density correction data Dr4 based on the detection signal S2 that has detected the composite correction pattern P ′.

  Subsequently, a correction example of the color image forming apparatus 100 according to the present invention will be described. FIG. 8 is a flowchart illustrating a correction example in the color image forming apparatus 100. In this embodiment, the combined correction patterns P and P ′ are formed on the intermediate transfer belt 6 so as to form a line and then detected as one detection signal S2, and correction processing of color misregistration and image density is performed serially. Take as an example.

  First, in step A <b> 1, the image forming unit 10 forms composite correction patterns P and P ′ on the intermediate transfer belt 6. In this example, 20 composite correction patterns P and 4 composite correction patterns P ′ are formed in a line. As shown in FIG. 2B, the image forming unit 10 changes the composite density correction pattern P from the first density Y, M, C, K color pattern having the lowest density of the image density correction pattern P2 to the highest fifth density. The Y, M, C, and K color patterns are sequentially formed. Thereafter, the composite correction pattern P ′ shown in FIG. 3B is formed with the highest sixth density.

  Next, in step A2, the image detection sensor 12 simultaneously detects all the combined correction patterns P and P 'and outputs one detection signal S2. This detection signal S2 is an analog signal having the waveform shown in FIGS. 6B and 7B, and its amplitude level is proportional to the image density of the image correction patterns P and P ′.

  In step A3, the control unit 15 samples the detection signal S2, reads the amplitude data Ls in each time data Ts as sampling data Ds (Ts, Ls), and stores it in the internal RAM 18. The sampling data Ds is obtained by converting the detection signal S2 that is an analog signal into digital data, as shown in FIG.

  In step A4, the CPU 17 of the control unit 15 compares the amplitude data Ls of the sampling data Ds stored in the RAM 18 with the threshold value Lth. As shown in FIG. 6B, the threshold Lth is set to an amplitude level (L1 <Lth <L2) at which the edge of the color misregistration correction pattern P1 can be detected.

  In step A5, the CPU 17 extracts sampling data Ds whose amplitude data Ls matches the threshold value Lth. Since the sampling data Ds extracted here is obtained by detecting the edges of the composite correction patterns P and P ′, it is hereinafter referred to as edge detection data De (Te, Ls). As shown in FIGS. 6B and 7B, four edge detection data De are extracted in one pattern for the combined correction pattern P and six in one pattern for the combined correction pattern P ′. Here, the edge detection data De related to the composite correction pattern P 'includes data obtained by detecting the edge of the image density correction pattern P2'.

  In step A6, the CPU 17 monitors whether comparison / extraction for all sampling data Ds has been completed. If not, the process returns to step A4, and if completed, the process proceeds to step A7.

  In step A7, the CPU 17 further extracts edge detection data De used for color misregistration correction from the edge detection data De extracted in step A5. The edge detection data De (four per pattern) related to the composite correction pattern P shown in FIG. 6B is obtained by detecting the edges of the color misregistration correction pattern P1. Therefore, the CPU 17 may extract all the edge detection data De as it is.

  On the other hand, the edge detection data De (six per pattern) related to the composite correction pattern P ′ shown in FIG. 7B includes data obtained by detecting the edge of the image density correction pattern P2 ′. The data can be obtained from Equation 4 and Equation 5. Therefore, the CPU 17 extracts the edge detection data De excluding those related to Equations 4 and 5.

  Here, the CPU 17 distinguishes the edge detection data De related to the composite correction pattern P from the edge detection data De related to P ′ based on the number or the like. For example, in this embodiment, 80 edge detection data De are extracted for the composite correction pattern P (4 edges × 4 color toner agents × 5 density per pattern). Accordingly, the edge detection data De1 to De80 relate to the composite correction pattern P, and the edge detection data De81 and subsequent ones relate to the composite correction pattern P ′.

  In step A8, the CPU 17 extracts image density correction data. For that purpose, it is necessary to read again the sampling data Ds including the information of the image density components of the image density correction patterns P2 and P2 'from all the sampling data Ds stored in the RAM 18 in step A3. For this purpose, the CPU 17 first further extracts data from which the edges of the image density correction patterns P2 and P2 'are detected from the edge detection data De extracted in step A5. The data number can be obtained from Equations 2 to 5. The edge detection time De of the edge detection data De according to the extracted Expressions 2 and 3, 4 and 5 is obtained, and images of the image density correction patterns P2 and P2 ′ between the two edges based on that time The sampling data Ds including the density component information is read again from the RAM 18 (extracted).

  In step A9, the CPU 17 calculates the current color misregistration amount (transfer position). If the intermediate transfer belt 6 is moved and scanned at a constant speed, the edge detection time Te of the edge detection data De extracted in step A7 is proportional to the widths and transfer positions of the color misregistration correction patterns P1 and P1 ′. . Therefore, the calculation is performed based on the edge detection time Te.

  In step A10, the CPU 17 compares the calculation result in step A9 with the target value, and calculates / outputs color misregistration correction data Dr3. The color misregistration correction data Dr3 indicates the difference between the current value of color misregistration and the target value as a correction amount, and the output color misregistration correction data Dr3 is mainly input to the laser writing unit 3 of the image forming unit 10. Thus, it is used for color misregistration correction.

  In step A11, the CPU 17 calculates the current image density. The amplitude data Ls of the sampling data Ds extracted in step A8 is proportional to the image density of the image density correction patterns P2 and P2 '. The CPU 17 obtains an average value of the amplitude data Ls of the extracted sampling data Ds for each of the image density correction patterns P2 and P2 '. At that time, in order to remove data near the edge, data including noise, etc., an operation is performed so as to obtain an average value after removing the protruding values.

  In step A12, the CPU 17 compares the calculation result in step A11 with the target value, and calculates / outputs image density correction data Dr4. The image density correction data Dr4 indicates the difference between the current value of the image density and the target value as a correction amount, and the output image density correction data Dr4 is mainly input to the developing unit 4 for image density correction. Will be used.

  In step A13, the image forming unit 10 is corrected based on the color misregistration correction data Dr3 and image density correction data Dr4 calculated / output in step A10 and step A12 described above. The laser writing unit 3 corrects the irradiation position of the laser beam applied to the photosensitive drums 1Y to 1K based on the input color misregistration correction data Dr3. The developing unit 4 corrects the toner agent adhesion amount based on the input image density correction data Dr4. In this way, a series of correction processing ends.

  In this example, the correction processing related to the color misregistration correction data Dr3 and the image density correction data Dr4 is serially performed. However, both corrections are performed after the sampling in step A3 and the extraction of the edge detection data De in step A6. Processing may be performed in parallel.

  Further, in order to more accurately distinguish the edge detection data De related to the composite correction pattern P and the edge detection data De related to P ′ performed in Step A7, for example, before Step A7, each edge detection data De A step for analyzing the interval of the edge detection time Te and distinguishing the two may be provided.

  Further, the control unit 15 inputs the color misregistration correction data Dr3 and the image density correction data Dr4 representing the correction amount to the image forming unit 10 and simultaneously stores them in a non-illustrated non-volatile memory so that they can be used for the next correction. It may be.

  As described above, according to the composite printed image as the embodiment according to the present invention, the color misregistration correction pattern P1 formed by the two sides and the predetermined area in contact with the color misregistration correction pattern P1 are formed with a different density from the color misregistration correction pattern P1. The image density correction pattern P2 is provided. Accordingly, since the color misregistration correction pattern P1 can be used for color misregistration correction and the image density correction pattern P2 can be used for image density correction, the composite correction pattern P in which the density of the image density correction pattern P2 is lowered for low density correction. In this case, the color misregistration correction pattern P1 is formed with a sufficient density, and an edge for color misregistration correction can be detected with high accuracy.

  According to the image forming apparatus as an embodiment of the present invention, for example, the color from the combined correction patterns P and P ′ formed / detected on the intermediate transfer belt 6 during a series of correction processes performed when the power is turned on. The information on the shift correction patterns P1 and P1 ′ is extracted to perform color shift correction, and the information on the image density correction patterns P2 and P2 ′ is extracted to perform image density correction. The invention is applied. Accordingly, since the color misregistration correction pattern P1 can be used for color misregistration correction and the image density correction pattern P2 can be used for image density correction, in the composite correction pattern in which the density of the image density correction pattern P2 is lowered for low density correction. However, the color misregistration correction pattern P1 is formed with a sufficient density, and an edge for color misregistration correction can be detected with high accuracy.

  Further, since correction patterns for color misregistration detection and image density detection can be simultaneously formed / detected, the time required for a series of correction processes can be shortened. Therefore, the productivity of the image forming apparatus can be improved.

  Further, as compared with the conventional case where the color misregistration correction pattern P1 and the image density correction pattern P2 are separately formed / detected, the edge of the image density correction pattern P2 can be detected with high accuracy, so that the image density correction can be performed efficiently. Can be extracted. Therefore, the image density correction pattern P2 can be formed in a small area to reduce the amount of toner agent used for the correction process.

  The present invention includes a tandem type color printer, a color copying machine, and a color complex machine having a photosensitive drum and an intermediate transfer belt, which perform image color misregistration and image density correction processing when the power is turned on, for example. It is very suitable to apply.

1 is a conceptual diagram illustrating a configuration example of a color image forming apparatus 100 as an embodiment. (A) And (B) is a figure which shows the structural example of the synthetic | combination correction pattern P which concerns on an Example. (A) And (B) is a figure which shows the structural example of the synthetic | combination correction pattern P 'based on an Example. 2 is a block diagram illustrating a configuration example of a correction processing system of the color image forming apparatus 100. FIG. (A)-(H) are the figures which show the example of sampling of detection signal S2 in the signal processing part 16. FIG. (A) And (B) is the top view and waveform diagram which show the data extraction example (the 1) of the control part 15. FIG. (A) And (B) is the top view and waveform diagram which show the data extraction example (the 2) of the control part 15. FIG. 5 is a flowchart illustrating an example of correction in the color image forming apparatus 100.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Charger, 3 ... Laser writing unit, 4 ... Developing unit, 6 ... Intermediate transfer belt, 7 ... Transfer roller, 10 ... Image Forming unit, 12 ... image detection sensor, 15 ... control unit, 16 ... signal processing unit, 17 ... CPU, 18 ... RAM, 100 ... color image forming apparatus

Claims (4)

In the composite printed image formed on the image carrier during color misregistration correction and image density correction processing of the image forming apparatus,
When the direction parallel to the rotation axis of the image carrier is the main scanning direction, and the direction in which the image carrier rotates is the sub-scanning direction,
Formed of two sides having a predetermined width and made to contact one end at a predetermined angle with each other;
The first side is formed by a straight line portion that is parallel to the main scanning direction,
Formed by the inclined portion second side are both made obliquely with respect to the main scanning direction or the sub-scanning direction, and the first indicia image that will be detected in accordance with the color misregistration correction processing of the image forming apparatus ,
On the inner angle side of the linear portion and the inclined portion that form two sides with the first mark image, a predetermined area having a distance for identification from the first mark image has the same density as the first mark image. formed, synthesized indicia image, characterized in that it comprises a second indicia image that will be detected according to the image density correction process of the image forming apparatus. The first and second mark images are:
It formed on the image bearing member simultaneously when the color shift correction process of the image forming apparatus and the time of image density correction processing, synthesis indicia image to claim 1 serial mounting, characterized in Rukoto simultaneously detected. In an image forming apparatus that forms a mark image of each color according to image information and superimposes the color image of each color to form a multicolor mark image on an image carrier.
An image forming means for forming a composite mark image including a first mark image and a second mark image on the image carrier;
Detecting means for detecting the composite seal image formed on the image carrier by the image forming means;
Control means for extracting the information of the first mark image from the composite mark image detected by the detection means and performing color shift correction, and extracting the information of the second mark image and correcting the image density. It equipped with a door,
When the direction parallel to the rotation axis of the image carrier is the main scanning direction, and the direction in which the image carrier rotates is the sub-scanning direction,
The first mark image is
Formed of two sides having a predetermined width and made to contact one end at a predetermined angle with each other;
The first side is formed by a straight line portion that is parallel to the main scanning direction,
The second side is formed by an inclined portion that is inclined with respect to the main scanning direction or the sub-scanning direction, and is detected according to the color misregistration correction processing of the image forming unit,
The second mark image is
On the inner angle side of the linear portion and the inclined portion that form two sides with the first mark image, a predetermined area having a distance for identification from the first mark image has the same density as the first mark image. is formed, the image forming apparatus according to claim Rukoto detected according to the image density correction process of the image forming means. A series of correction processes by the image forming unit, the detection unit, and the control unit are:
When the image forming apparatus is turned on and / or
When the power saving mode for reducing the power consumption during the waiting time of the image forming apparatus is canceled and / or
The image forming apparatus according to claim 3, wherein the image forming apparatus is executed when maintenance performed regularly or irregularly in the image forming apparatus is completed.

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