JP2007310322A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately correct an image position by a registration pattern for inspection with an image forming apparatus. <P>SOLUTION: In a state where an image is not formed on an intermediate transfer belt 5 in the image forming apparatus, the surface reflection is detected by a position detector 6, and the surface state data is obtained. Positional data such as the surface state data deviated from a threshold is stored as a noise feature amount. The registration pattern for inspection is formed on the intermediate transfer belt 5, and pattern data is obtained from the reflection data on the registration pattern for inspection. The pattern data is corrected by using the noise feature amount, then, the edge position of the pattern data is obtained. Color misalignment is corrected based on the edge position. Such a failure is prevented that the position of the registration pattern for inspection is erroneously detected, irrespective of dust and dirt on the intermediate transfer belt 5, consequently, the image position is accurately and stably corrected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus such as a digital copying machine or a laser printer that forms a color image using electrophotographic technology.

  In an electrophotographic apparatus having a plurality of photoconductive drums, if the positions of the respective laser beams do not coincide with each other, the positions of the toner images are shifted when the images of the photoconductive drums are superimposed, and the image quality is reduced. It will decline. Causes of positional deviation of the toner images of the respective colors include registration deviation in the sub-scanning direction, inclination in the main scanning direction, registration deviation in the main scanning direction, and magnification error in the main scanning direction. When correction control is performed for these shifts, generally, a plurality of single-color resist patterns are written on an image carrier made of an intermediate transfer member to form an image position detection pattern. By detecting the position of the resist pattern, the amount of positional deviation of each image of each color is detected, and the writing position is corrected. Hereinafter, some examples of related art will be given.

  The “image forming apparatus” disclosed in Patent Document 1 is an image forming apparatus that can prevent a scratch from appearing in an image even when the intermediate transfer member is damaged by using a long intermediate transfer member. is there. The toner image on the photosensitive member is transferred to the intermediate transfer member by primary transfer means. The toner image transferred to the intermediate transfer member is transferred to transfer paper by a secondary transfer unit. The primary transfer means includes at least one position detection mark and a position detection means for detecting the position detection mark in a region where no image is initially formed. It also has a flaw detection means for detecting flaws generated on the intermediate transfer member.

The “image forming apparatus” disclosed in Patent Document 2 eliminates color misregistration of a transferred image caused by fluctuations in the moving speed of an intermediate transfer belt or the like. At this time, color misregistration of the transferred image due to unclearness or scratches on the mark on the belt is eliminated. A sheet or toner image is carried, and the moving speed of an endless belt marked with a predetermined interval is detected. Control the moving speed to be constant. The transfer position deviation of the toner image onto the paper or endless belt is controlled. The moving speed of the mark is detected, and the control amount of the belt that reaches the preset target speed is calculated and acquired based on the moving speed. The belt speed is controlled by this control amount until the next mark. When the mark is unclear, the control amount of the previous mark is maintained. When there is dirt or a flaw, the control amount is not calculated or acquired based on these, and the control amount of the previous mark is maintained and the speed control is performed.
JP 2003-76100 A Japanese Patent Laid-Open No. 2004-21236

  However, the conventional image position correction method has the following problems. If there is a scratch or dust or the like on the intermediate transfer member, the reflected signal from the scratch or dust is mistaken for the edge signal of the resist pattern, and the position of the resist pattern is erroneously detected. For this reason, the image position cannot be corrected correctly and color misregistration occurs.

  An object of the present invention is to solve the above-described conventional problems, and in an image forming apparatus, the position of a resist pattern for image position inspection can be accurately determined even when there is a scratch or dust on the intermediate transfer member. And correcting the image position.

  In order to solve the above problems, in the present invention, an image forming apparatus includes a photosensitive image carrier, charging means for charging the image carrier, and exposure for forming an electrostatic latent image on the charged image carrier. Means, developing means for supplying a developer to the image carrier to visualize the electrostatic latent image, transfer means for transferring the visualized image from the image carrier, and forming an inspection resist pattern on the transfer means Detecting means for detecting light reflection from the transfer means and outputting a reflection detection signal; detecting the output level of the reflection detection signal when the transfer means has no image; and outputting surface state data and for inspection Level detection means for detecting the output level of the reflection detection signal from the resist pattern and outputting pattern data, noise feature quantity detection means for obtaining a noise feature quantity from the surface state data, and a feature for storing the noise feature quantity And amount storage means, and configured to and a correcting means for correcting the pattern data using the noise characteristic amount.

  With the configuration described above, color misregistration correction can be performed accurately and stably in the image forming apparatus.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to FIGS.

  The embodiment of the present invention detects the noise position of reflection data in the state where there is no image on the intermediate transfer belt as a noise feature amount, corrects the reflection data of the inspection resist pattern using the noise feature amount, and performs inspection. The image forming apparatus corrects the image position by obtaining the accurate position of the resist pattern for use.

  FIG. 1 is a conceptual diagram schematically showing the basic configuration of an image forming apparatus in an embodiment of the present invention. In FIG. 1, a photosensitive drum 1 is a photosensitive image carrier. The charger 2 is a means for charging the photosensitive drum (image carrier). The laser 3 is an exposure means for forming an electrostatic latent image on a charged image carrier. The developing device 4 is a means for visualizing the latent image with a developer (toner). The intermediate transfer belt 5 is a means for transferring an image from an image carrier to printing paper. The position detector 6 is a reflective optical sensor that detects the state of the intermediate transfer belt.

  FIG. 2 is a functional block diagram illustrating a basic configuration of the image forming apparatus. In FIG. 2, a polygon mirror 7 is means for reflecting laser light and performing scanning in the main scanning direction. The Fθ lens 8 is means for scanning the laser beam at a constant speed. The folding mirror 9 is means for reflecting the laser beam at the tip of the image. The synchronization detection unit 10 is means for detecting an image writing position. The first detector 11 is a first means for detecting light reflection from the intermediate transfer belt and outputting a reflection detection signal. The second detector 12 is a second means for detecting light reflection from the intermediate transfer belt and outputting a reflection detection signal. The level detection means 13 is means for detecting the level of the reflection detection signal and converting it into a digital signal. The noise feature amount detection unit 14 is a means for obtaining a noise feature amount such as a noise position from reflection data in a state where there is no image on the intermediate transfer belt. The feature amount storage unit 15 is a memory that stores noise feature amounts. The section setting register 16 is a register for setting a section width for obtaining a moving average. The threshold setting register 17 is a register that sets a threshold for determining noise. The edge information storage unit 18 is a memory that stores edge information of a resist pattern.

  FIG. 3 is a diagram showing the formation state of the resist pattern for detecting the image position and the position of the detection device. FIG. 4 is a flowchart showing a processing procedure of the edge detection method of the resist pattern. FIG. 5 is a graph showing the waveform of the surface state data obtained by converting the reflection data when there is no image on the intermediate transfer belt by the AD converter. FIG. 6 is a graph showing the moving average value of the surface state data. The horizontal axis is the position, and the vertical axis is the level. FIG. 7 is a flowchart showing a processing procedure of another edge detection method for a resist pattern. FIG. 8 is a flowchart showing a processing procedure of still another edge detection method for a resist pattern.

  The function and operation of the image forming apparatus in the embodiment of the present invention configured as described above will be described. First, an overview of the functions of the image forming apparatus will be described with reference to FIG. A position detector 6 detects the state of the intermediate transfer belt 5. Color misregistration correction is performed based on the detection result. The charger 2 charges the photosensitive drum 1 as an image carrier. An electrostatic latent image is formed on the charged photosensitive drum 1 by a laser 3 as exposure means. The developing unit 4 visualizes the latent image with a developer (toner). An image is transferred from the photosensitive drum 1 to an intermediate transfer belt 5 which is a transfer means, and further transferred to a printing paper.

  Next, functions of the image forming apparatus will be described with reference to FIG. Laser light emitted from the laser 3 (LD laser diode) is reflected by the rotating polygon mirror 7 and performs scanning in the main scanning direction. The reflected laser light passes through the Fθ lens 8 in order to scan at a constant speed on the image carrier. The laser beam at the tip of the image is reflected by the folding mirror 9 and applied to the synchronization detection unit 10. The synchronization detection unit 10 is provided with a light receiving element, and when the light receiving element is irradiated with laser light, it is converted into an electrical signal, and the image writing position can be detected. The writing position for main scanning is determined based on the writing position.

  In order to examine the scratches on the intermediate transfer belt, the first detector 11 and the second detector 12 detect light reflection from the intermediate transfer belt in the absence of an image to obtain a reflection detection signal. Level detection means 13 detects the level of the reflection detection signal, converts it to a digital signal, and outputs surface state data. The noise feature quantity detection unit 14 obtains a noise feature quantity such as a noise position from the surface state data. At this time, the moving average is obtained by averaging the sections set in the section setting register 16, and the noise position is determined based on the threshold set in the threshold setting register 17. The feature quantity storage unit 15 stores the noise feature quantity. A resist pattern for inspection is formed on the intermediate transfer belt 5, and the first detector 11 and the second detector 12 detect light reflection from the intermediate transfer belt 5 and output a reflection detection signal. The level detection means 13 detects the output level of the reflection detection signal and outputs pattern data. The pattern data is corrected using the stored noise feature amount. The edge of the resist pattern is obtained from the corrected pattern data, and the edge information is stored in the edge information storage unit 18.

  Next, a resist pattern for image position detection will be described with reference to FIG. As shown in FIGS. 2 and 3, a plurality of detection means are provided. As an example, a case where two detection means, that is, a first detection means and a second detection means are provided is shown. By writing a plurality of single-color resist patterns and detecting the position of the resist pattern, the amount of misregistration of each image of each color is detected, and the writing position is corrected using the output information of each color.

  Next, a processing procedure for detecting the edge of the resist pattern will be described with reference to FIGS. 4, 5, and 6. Before forming the resist pattern, in step 1, the surface state of the intermediate transfer belt is detected. That is, the reflected light from the surface of the intermediate transfer belt is detected by the first detector and the second detector in FIG. The level of the voltage output from the detector is determined by the level detection means. As an example, a case where an AD converter is used to convert to discrete data will be described. FIG. 5 shows an example of an output waveform of the AD converter when noise is mixed due to scratches, dust or the like on the intermediate transfer belt.

The surface state data output from the AD converter is input to the noise feature amount detection unit 14 to detect the noise feature amount. The surface state data input to the noise feature quantity detection unit 14 is Nj. j is a subscript indicating a sampling point, and is 0, 1, 2, 3,. Furthermore, when detecting the average level of the surface state data in a certain section, the moving average value Ai is calculated by the equation (1).
Ai = Σ _{j = in} ^{i + n} (Nj / (2n + 1)) (1)
Here, i is a sampling point at a certain time point, and (2n + 1) is the number of samples in the section. An interval setting register 16 is prepared so that the average level detection interval can be changed.

  When the moving average value is obtained from the surface state data shown in FIG. 5, a graph shown in FIG. 6 is obtained. The moving average value shown in FIG. 6 is cut at a certain threshold (for example, 2) to detect noise. Data that is 2 or less in the graph of FIG. 6 is detected as noise. The sampling position is stored in the feature amount storage unit 15 as a noise feature amount. This detection operation is performed over one rotation of the intermediate transfer belt. A threshold setting register 17 is prepared so that the threshold can be changed. That is, in step 2, it is checked whether it is smaller than the threshold value. If it is smaller than the threshold value, the position information is stored in the feature amount storage unit 15 in step 3. In step 4, the process is repeated over one turn of the intermediate transfer belt.

  After storing the noise feature amount, a resist pattern is formed in step 5, and in step 6, the state of the intermediate transfer belt is detected to detect the edge of the resist pattern. If an edge is detected in step 7, it is determined in step 8 whether or not the detected edge is due to noise based on the stored noise sampling position. If it is determined that it is equivalent to the stored sampling position, the edge is attributed to noise and is excluded from the position information of the resist pattern in step 9. If it differs from the noise sampling position, it is stored in the edge information storage unit 18 as position information of the resist pattern in step 10. In step 11, repeat until all edges are detected.

  Next, as another example, a method for storing sampling data as a noise feature amount will be described with reference to FIG. Before forming the resist pattern, in step 12, the state of the intermediate transfer belt is detected. The sampling data (surface state data) at that time is stored in the feature quantity storage unit 15 as a noise feature quantity Ni in step 13. This detection operation is also performed over one turn or more of the intermediate transfer belt.

After storing the noise feature amount, a resist pattern is formed in step 15, and the state of the intermediate transfer belt is detected in step 16 to detect the edge of the resist pattern. The sampling data (pattern data) of the resist pattern for edge detection is Ri. i is a subscript indicating a sampling point, and is 0, 1, 2, 3,. In step 17, edge detection data Di is obtained from equation (2), and in step 18, edge detection is performed. In step 19, the edge position is stored in the edge information storage unit 18.
Di = Ri-Ni (2)

  Next, referring to FIG. 8, as another example, a method for storing a noise position and sampling data as a noise feature amount will be described. In step 21, the surface state of the intermediate transfer belt is detected. After the moving feature value is obtained by the noise feature quantity detection unit 14, noise detection is performed with a certain threshold value. Data that is 2 or less in the graph of FIG. 6 is detected as noise. The sampling position and sampling data (data before moving average) at that time are stored in the feature amount storage unit 15 as a noise feature amount. This detection operation is also performed over one turn or more of the intermediate transfer belt. That is, in step 22, it is checked whether it is smaller than the threshold value. If it is smaller than the threshold value, the position information is stored in the feature amount storage unit 15 in step 23. In step 24, the process is repeated over one or more turns of the intermediate transfer belt.

After storing the noise feature amount, a resist pattern is formed in step 25, and in step 26, the state of the intermediate transfer belt is detected to detect the edge of the resist pattern. The sampling data (pattern data) of the resist pattern for edge detection is Ri. i is a subscript indicating a sampling point, and is 0, 1, 2, 3,. In step 27, it is checked whether it is a noise position. If it is determined that the stored sampling position is the same as the stored noise sampling position, edge detection data Di is obtained in step 28 using equation (3).
Di = Ri-Ni (3)
If it is not determined to be equal to the stored sampling position of the noise, the pattern data Ri is set as edge detection data Di in step 29 as shown in equation (4).
Di = Ri (4)
Using this Di, edge detection processing is performed in step 30. By performing this operation, erroneous detection due to scratches or dust on the intermediate transfer belt can be prevented, and color misregistration correction can be performed stably.

  As described above, in the embodiment of the present invention, the image forming apparatus detects the noise position of the reflection data when there is no image on the intermediate transfer belt as the noise feature amount, and the reflection data of the inspection resist pattern is detected as noise. Since the correction is performed using the feature amount to obtain the accurate position of the inspection resist pattern and the image position is corrected, the color misregistration correction can be stably performed.

  The image forming apparatus of the present invention is optimal for accurately performing color misregistration correction in a digital copying machine, a laser printer, or the like that forms a color image using electrophotographic technology.

1 is a conceptual diagram illustrating a basic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a functional block diagram illustrating a basic configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the formation state of the resist pattern of the image forming apparatus in the Example of this invention, and the position of a detection apparatus. 6 is a flowchart illustrating a processing procedure of a color misregistration correction method in the image forming apparatus according to the exemplary embodiment of the present invention. FIG. 4 is a diagram illustrating surface state data of an intermediate transfer belt of the image forming apparatus according to the exemplary embodiment of the present invention. It is a figure which shows the moving average value of the surface state data in the image forming apparatus in the Example of this invention. 6 is a flowchart showing a processing procedure of another color misregistration correction method in the image forming apparatus in the embodiment of the present invention. 10 is a flowchart showing a processing procedure of still another color misregistration correction method in the image forming apparatus according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Charger, 3 ... Laser, 4 ... Developing device, 5 ... Intermediate transfer belt, 6 ... Position detector, 7 ... Polygon mirror , 8 ... lens, 9 ... mirror, 10 ... synchronization detector, 11 ... first detector, 12 ... second detector, 13 ... level detecting means, 14 ... Noise feature amount detection unit, 15 ... feature amount storage unit, 16 ... section setting register, 17 ... threshold setting register, 18 ... edge information storage unit.

Claims (18)

  A photosensitive image carrier, a charging unit for charging the image carrier, an exposure unit for forming an electrostatic latent image on the charged image carrier, and a developer supplied to the image carrier to supply an electrostatic latent image. Developing means for visualizing an image; transfer means for transferring the visualized image from the image carrier; means for forming a resist pattern for inspection on the transfer means; and detecting light reflection from the transfer means Detecting means for outputting a reflection detection signal; detecting an output level of the reflection detection signal in a state where there is no image on the transfer means; outputting surface state data; and outputting an output level of the reflection detection signal from the resist pattern for inspection. Level detection means for detecting and outputting pattern data; noise feature quantity detection means for obtaining a noise feature quantity from the surface state data; feature quantity storage means for storing the noise feature quantity; An image forming apparatus characterized by comprising a correction means for correcting the pattern data using the noise characteristic amount.   The image forming apparatus according to claim 1, wherein the noise feature amount detection unit is a unit that obtains the noise feature amount over a predetermined section of the transfer unit.   3. The image forming apparatus according to claim 2, wherein the predetermined section is equal to or more than one turn of the transfer unit.   The noise feature quantity detection means includes means for obtaining a moving average value of the surface state data, means for comparing the moving average value and a threshold value, and means for obtaining a noise feature quantity based on a comparison result. The image forming apparatus according to claim 1, wherein:   The image forming apparatus according to claim 4, wherein the noise feature amount detection unit includes a unit that changes a section width for obtaining the moving average value.   The image forming apparatus according to claim 5, wherein the noise feature amount detection unit includes a storage unit that stores the threshold value.   The image forming apparatus according to claim 1, wherein the noise feature amount is information indicating a position on the transfer unit corresponding to noise included in the surface state data.   The image forming apparatus according to claim 1, wherein the noise feature amount is information relating to an output level of noise included in the surface state data.   2. The noise feature amount is information indicating a position on the transfer unit corresponding to noise included in the surface state data and information regarding an output level of noise included in the surface state data. The image forming apparatus described.   A photosensitive image carrier, a charging unit for charging the image carrier, an exposure unit for forming an electrostatic latent image on the charged image carrier, and a developer supplied to the image carrier to supply an electrostatic latent image. An image forming control method in an image forming apparatus, comprising: a developing unit that visualizes an image; and a transfer unit that transfers the visualized image from the image carrier. The surface state data is obtained by detecting the light reflection of the surface, the noise feature amount is obtained and stored from the surface state data, the inspection resist pattern is formed on the transfer means, and the light reflection of the inspection resist pattern is detected. An image formation control method comprising: obtaining pattern data and correcting the pattern data using the noise feature amount.   The image formation control method according to claim 10, wherein the surface state data is obtained over a predetermined section of the transfer unit.   12. The image forming control method according to claim 11, wherein the predetermined section is equal to or longer than one turn of the transfer unit.   The image formation control method according to claim 10, wherein a moving average value of the surface state data is obtained, and a noise feature amount is obtained based on a result of comparing the moving average value and a threshold value.   14. The image forming control method according to claim 13, wherein a section width for obtaining the moving average value is changed according to set information.   The image forming control method according to claim 14, wherein a predetermined value is stored as the threshold value.   The image forming control method according to claim 10, wherein the noise feature amount is information indicating a position on the transfer unit corresponding to noise included in the surface state data.   The image formation control method according to claim 10, wherein the noise feature amount is information relating to an output level of noise included in the surface state data.   11. The noise feature amount is information indicating a position on the transfer unit corresponding to noise included in the surface state data and information regarding an output level of noise included in the surface state data. The image formation control method as described.

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