JP5365439B2 - Image forming apparatus and color misregistration correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and inexpensively perform accurate color deviation correction in a short time without being affected by scratch or foreign matter on an image carrier or irregularities of the surface thereof. <P>SOLUTION: The pattern for color deviation correction includes color patterns of the same color, which are formed on the downstream side and upstream side in a carrying direction of an intermediate transfer belt with a certain given space, wherein each of the color patterns is composed of a reference color and a plurality of non-reference colors, and each color pattern is disposed adjacently along the carrying direction of the intermediate transfer belt. A spacing position constituted by each color pattern is detected to calculate a color deviation amount, and a color deviation correction amount is calculated from the color deviation amount to perform color deviation correction. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

The present invention relates to an image forming apparatus and a color misregistration correction method , and more particularly to an image forming apparatus and a color misregistration correction method for correcting color misregistration between colors in a tandem color image forming apparatus.

  Conventionally, as a dandem type color image forming apparatus, yellow (Y), magenta (M), cyan (C), and black (K) writing units (image forming units) are provided, and the writing units are generated by such writing units. A color image of a different color is sequentially superimposed on an image carrier such as an intermediate transfer belt, and a full color image is formed by transferring the color image formed on the image carrier to a transfer medium such as paper. It is generally known what to do.

  In this tandem type color image forming apparatus, when an image generated by a writing unit different for each color is transferred to an intermediate transfer belt, for example, if a slight color shift occurs in the sub-scanning direction, which is the paper transport direction, each color A so-called color shift occurs in which the pixel positions overlap with each other. Causes of color misregistration include misalignment caused by temperature changes of various writing unit components such as rollers and reflection mirrors, as well as misalignment of replacement parts of the color image forming apparatus.

  For this reason, conventionally, a specific color misregistration correction pattern is formed on a transfer belt before image formation, and correction processing is performed to suppress the occurrence of color misregistration of each color using the color misregistration correction pattern. It has been known. This type of color misregistration correction technology calculates the amount of color misregistration between colors by forming a toner pattern of each color on a transfer belt and detecting the toner pattern with a regular reflection light sensor. Therefore, color misregistration correction control is executed.

  FIG. 16 is a diagram illustrating a color misregistration correction pattern including a conventional standard color and a single color pattern of a plurality of non-reference colors, and the problem. The color misregistration correction pattern shown in FIG. 16 includes a linear pattern orthogonal to the belt conveyance direction and a diagonal line pattern that forms an inclination angle with respect to the belt conveyance direction. A predetermined interval is provided for each of yellow (Y), magenta (M), and cyan (C). As described above, the conventional single color pattern formed on the transfer belt is detected by using a regular reflection light sensor, calculates the position of each color pattern, compares the position of each color pattern with the reference position, and performs color misregistration. The color matching control is performed by calculating the amount and feeding back the color misregistration amount to the writing control.

  The inspection image pattern in Patent Document 1 employs a pattern that is almost the same as that in FIG. 16 described above. If there is a scratch (or foreign matter or surface irregularities) on the belt surface between the monochromatic patterns, the pattern is incident on the regular reflection light sensor. Since the light to be diffused is reflected light, the pattern interval “A” should be detected, but there is a risk of erroneous detection as an incorrect pattern interval “B”. When color misregistration correction control based on this erroneous detection is executed, unexpected color misregistration correction control is executed, which may cause a larger color misregistration. Therefore, in Patent Document 1, feature points such as scratches on the transfer belt before image formation, foreign matter, and surface irregularities are detected in advance, and the feature point information is stored, so that the feature points or feature points are stored. By forming the inspection image pattern at the avoided position, even if there is a scratch on the transfer belt, highly accurate color misregistration correction without erroneous detection has been performed.

  FIG. 17 is a diagram showing an example of a conventional misregistration correction pattern, and FIG. 18 is a waveform for explaining edge detection of each color pattern using the sensor output waveform and the threshold level of the misregistration correction pattern of FIG. FIG. In Patent Document 2, as shown in FIG. 17, as a toner pattern used for misregistration correction, a small non-reference color (magenta: 25M_Y, cyan: 25C_Y) on a pattern of a large reference color (black: 25BK --_ T1). , Yellow: 25Y_Y) on the pattern of the next large reference color (black: 25BK --_ T2) with a predetermined interval formed in a direction orthogonal to the belt conveyance direction (arrow direction in the figure). The patterns of small non-reference colors (magenta: 25M_S, cyan: 25C_S, yellow: 25Y_S) are formed so as to be inclined with respect to the belt conveyance direction. This is formed as one pattern, and is repeatedly formed for a plurality of patterns in the belt conveyance direction, and further formed in three rows in parallel in the belt conveyance direction. The interval between the large reference color is alternately spaced in the direction orthogonal to the belt conveyance direction and in the inclined direction.

  When detecting the misalignment correction pattern shown in FIG. 17 by the TM sensors 17, 18, and 19, as shown in FIG. 18, a belt provided between the large reference color pattern and the next large reference color pattern. Since the exposed portion is detected using a regular reflection light sensor, waveforms with large amplitudes at both ends can be obtained. In addition, the small non-reference color pattern formed on the large reference color pattern detects the density difference between the reference color and the non-reference color by the diffuse reflected light sensor. can get. For this reason, in Patent Document 2, two types of sensors, that is, a regular reflection light sensor and a diffuse reflection light sensor, are required as sensors for detecting misalignment correction patterns.

  As described above, the misregistration correction pattern shown in Patent Document 2 forms the small non-reference color pattern on the large reference color pattern, thereby covering the belt surface as much as possible and reducing the exposed area of the belt surface. Therefore, even if there are scratches, foreign matter, or surface irregularities on the belt surface, the possibility of erroneously recognizing a misregistration correction pattern can be reduced.

  However, according to Patent Document 1 described above, when performing color misregistration correction, it is necessary to detect in advance a feature point such as a scratch on the transfer belt, foreign matter, or surface irregularities before image formation. Applicable when it takes a long time, depending on the number and location of detected feature points, whether the inspection image pattern is formed on the feature points, avoiding the feature points, or removing or avoiding the feature points There is a problem in that it is necessary to determine whether to perform the inspection, and it takes time and labor to determine the formation position of the inspection image pattern.

  According to Patent Document 2, as shown in FIG. 17, a large reference color (25BK --_ T1) of a toner pattern used for positional deviation correction, and a subsequent large reference color (25BK --_ T2) Since the surface of the transfer belt is exposed, the interval portion inclined with respect to the belt conveyance direction between them needs to be detected by a regular reflection light sensor. Further, since the patterns of the small non-reference colors (magenta: 25M_Y, cyan: 25C_Y, yellow: 25Y_Y) formed on the pattern of the large reference color (25BK --_ T1) are all diffuse reflection light. It is necessary to detect with an optical sensor. As described above, detection of a toner pattern for correcting misregistration in Patent Document 2 requires two types of sensors, which is costly and increases the number of sensors, which may lead to erroneous detection due to characteristic variations. There was a problem that became high.

  Further, according to Patent Document 2, as shown in FIG. 18, the edge of the toner pattern is detected using two types of detection waveforms and threshold levels detected by the regular reflection light sensor and the diffuse reflection light sensor. In this case, it is necessary to set the threshold level according to the detection waveform of the non-reference color pattern with small amplitude, so the threshold level setting range is very narrow, and it may be difficult to set the threshold level depending on the situation or the sensor. There has been a problem that electrical noise is riding on the output and erroneous detection is likely to occur.

  According to Patent Document 2, as shown in FIG. 17, a pattern of small non-reference colors (magenta: 25M_Y, cyan: 25C_Y, yellow: 25Y_Y) extending in a direction orthogonal to the belt conveyance direction, and the belt A pattern of small non-reference colors (magenta: 25M_S, cyan: 25C_S, yellow: 25Y_S) extending in a direction inclined with respect to the transport direction is provided in one set of patterns. However, the interval inclined with respect to the belt conveyance direction between the large reference color (25BK --_ T1) and the next large reference color (25BK --_ T2) indicates one position of the reference color (black). However, since the interval extending in the direction perpendicular to the belt conveyance direction is not completed until the second set of patterns is formed, an extra pattern must be formed in the belt conveyance direction. There was a problem that toner was wasted.

The present invention has been made in view of the above, and it is simple and low-cost to perform high-precision color misregistration in a short time without being affected by scratches on the image carrier, foreign matter, or surface irregularities. An object of the present invention is to provide a color misregistration image forming apparatus and a color misregistration correction method that can be performed.

In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention is an image forming apparatus that forms a color image by superimposing a reference color and a plurality of non-reference color images. A pattern forming unit that forms a misregistration correction pattern on the image carrier, and detects each color pattern formed by a reference color and a plurality of non-reference colors of the color misregistration correction pattern formed on the image carrier. Detecting the edge of each color pattern based on the sampling waveform obtained by the sampling means and a predetermined threshold level, and calculating an intermediate point from the edge Pattern position detecting means for detecting the position of each color pattern, and each of the pattern positions detected by the pattern position detecting means Comparing the position of the pattern with the reference position to calculate the color misregistration amount, calculating means for calculating the color misregistration amount based on the color misregistration amount, and based on the color misregistration correction amount calculated by the calculating means Control means for controlling each part of the apparatus main body related to color misregistration, and performing color misregistration correction by controlling each part of the apparatus main body by the control means, and the color misregistration correction pattern has the same color pattern. The color patterns are respectively formed on the downstream side and the upstream side in the conveyance direction of the image carrier at a predetermined interval, and the color pattern is composed of the reference color and the plurality of non-reference colors, respectively. A portion of the reference color and the plurality of non-reference color color patterns adjacent to each other along the conveyance direction of the carrier overlaps with a predetermined width with respect to the conveyance direction of the image carrier. Characterized in that it is formed Te.

A color misregistration correction method according to the present invention is a color misregistration correction method executed by an image forming apparatus, and the image forming apparatus includes a pattern forming unit, a pattern detecting unit, a sampling unit, and a pattern position detecting unit. Means, a calculation means, and a control means, wherein the pattern forming means forms a color misregistration correction pattern on the image carrier, and the pattern detection means is formed on the image carrier. Detecting each color pattern formed by the reference color of the color misregistration correction pattern and a plurality of non-reference colors, the sampling means sampling the detection signal of the color misregistration correction pattern, and Pattern position detection means detects the edge of each color pattern based on the sampling waveform and a predetermined threshold level, and calculates an intermediate point from the edge The step of detecting the position of each color pattern and the calculation means compare the position of each color pattern with a reference position to calculate a color misregistration amount, and calculate a color misregistration correction amount based on the color misregistration amount. And a step of controlling each part of the apparatus main body related to color misregistration based on the color misregistration correction amount, controlling each part of the apparatus main body to perform color misregistration correction, and the color misregistration. The correction patterns are respectively formed on the downstream side and the upstream side in the conveyance direction of the image carrier at a predetermined interval with the same color pattern, and the color pattern includes the reference color and the plurality of non-reference colors. Each of the color patterns is arranged adjacently along the conveyance direction of the image carrier, and a portion where the color patterns of the reference color and the plurality of non-reference colors are adjacent to each other is conveyed by the image carrier. Is against the direction Characterized in that it is formed by overlapping of constant width.

  According to the present invention, the same color pattern is formed on the downstream side and the upstream side in the transport direction of the image carrier at a predetermined interval, and the color pattern is composed of a reference color and a plurality of non-reference colors, respectively. Since each color pattern is a color misregistration correction pattern having a shape arranged adjacently along the conveyance direction of the image carrier, most of the surface of the image carrier is covered with the color misregistration correction pattern. Thus, it is possible to perform highly accurate color misregistration correction in a short time and at a low cost without being affected by scratches on the image carrier, foreign matter, or surface irregularities.

  According to the invention, the color misregistration correction pattern is formed on the image carrier by the pattern forming means, each color pattern of the color misregistration correction pattern is detected by the pattern detection means, and the detection signal is detected by the sampling means. The pattern position detection means detects the edge of each color pattern based on the sampling waveform and a predetermined threshold level, calculates the intermediate point from the edge to detect the position of each color pattern, and the calculation means detects the pattern position. The position of each color pattern detected by the means is compared with the reference position to calculate the color misregistration amount, and the color misregistration correction amount is calculated based on the color misregistration amount, and the control means calculates the color misregistration amount based on the color misregistration correction amount. In order to perform color misregistration correction by controlling each part of the apparatus main body related to misregistration, a color misregistration correction pattern that covers most of the surface of the image carrier is used. It prevents affected by irregularities of scratches or foreign matter and the surface on the image bearing member, an effect that a highly accurate color misregistration correction in a short time can be carried out easily and inexpensively.

  According to the invention, the pattern forming unit forms a color misregistration correction pattern on the image carrier, and the pattern detection unit includes a plurality of reference colors of the color misregistration correction pattern formed on the image carrier. The color pattern formed by each non-reference color is detected, the sampling means samples the detection signal of the color misregistration correction pattern, and the pattern position detection means detects each color pattern based on the sampling waveform and a predetermined threshold level. An edge is detected, an intermediate point is calculated from the edge to detect the position of each color pattern, and the arithmetic means compares the position of each color pattern with a reference position to calculate a color misregistration amount. The color misregistration correction amount is calculated based on the color misregistration correction amount. The color misregistration correction pattern that covers most of the surface eliminates the effects of scratches on the image carrier, foreign matter, and surface irregularities, and enables highly accurate color misregistration correction in a short time and at a low cost. There is an effect that can be.

FIG. 1 is a diagram for explaining the shape of a color misregistration correction pattern according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a schematic configuration of the color copying machine according to the first embodiment. FIG. 3 is a D direction arrow diagram illustrating the optical device of FIG. FIG. 4 is a diagram illustrating the principle of a regular reflection light sensor that detects the surface state of the intermediate transfer belt in FIG. FIG. 5 is a block diagram of a component that performs color misregistration correction processing. FIG. 6 is a functional block diagram illustrating functions of the CPU of FIG. FIG. 7 is a diagram showing an example of forming a color misregistration correction pattern formed on the intermediate transfer belt in the first embodiment. FIG. 8 is a diagram for explaining a state in which a scratch on the belt is exposed at the same color pattern interval. FIG. 9 is a flowchart for explaining the color misregistration correction processing according to the first embodiment. FIG. 10 is a diagram showing a color misregistration correction pattern used in the second embodiment. FIG. 11 is a waveform diagram for explaining a settable range of the threshold level in the second embodiment. FIG. 12 is a diagram for explaining the relationship between the detection data of each color pattern and the color misregistration correction content. FIG. 13 is a diagram showing an example of forming a conventional color misregistration correction pattern. FIG. 14 is a flowchart for explaining the operation of the color misregistration correction process according to the second embodiment. FIG. 15 is an enlarged view of a pattern edge portion when the drawing resolution of the color misregistration correction pattern is changed by making it possible to select the light source used in the exposure apparatus. FIG. 16 is a diagram illustrating a color misregistration correction pattern including a conventional standard color and a single color pattern of a plurality of non-reference colors, and the problem. FIG. 17 is a diagram illustrating an example of a conventional misregistration correction pattern. FIG. 18 is a waveform diagram for explaining edge detection of each color pattern using the sensor output waveform and the threshold level of the positional deviation correction pattern of FIG.

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

(First embodiment)
FIG. 1 is a diagram for explaining the shape of a color misregistration correction pattern according to the first embodiment of the present invention. A color misregistration correction pattern 10 shown in FIG. 1 has color patterns of the same color on the downstream side and the upstream side in the conveyance direction of the intermediate transfer belt, which is an image carrier (in the direction of the white arrow in the figure), at a predetermined interval. Is formed. Here, the types of color patterns include black (K), which is a reference color, and yellow (Y), magenta (M), and cyan (C), which are a plurality of non-reference colors.

  For example, as shown in FIG. 1, a yellow (Y) rectangular toner pattern 10Yd is formed from the downstream side in the conveyance direction of the intermediate transfer belt, and a yellow ( A rectangular toner pattern 10Yu of Y) is formed. Then, for black (K), magenta (M), and cyan (C), similarly to the above-described yellow (Y), rectangular toner patterns 10Kd, 10Ku, 10Md, 10Mu, 10Cd, and 10Cu are formed. The patterns are arranged adjacent to each other along the belt conveyance direction. In this case, the intervals 10YR, 10KR, 10MR, 10CR formed by the respective color patterns form intervals extending in a direction orthogonal to the belt conveyance direction.

  A yellow (Y) triangular toner pattern 10Yd is formed adjacent to the rectangular toner pattern 10Cu, and a yellow (Y) triangular toner is upstream from the toner pattern 10Yd by a predetermined interval 10YS. A pattern 10Yu is formed. In this case, similarly to the above-described yellow (Y), triangular toner patterns 10Kd, 10Ku, 10Md, 10Mu, 10Cd, and 10Cu are formed for black (K), magenta (M), and cyan (C). The color patterns are arranged adjacent to each other along the belt conveyance direction. In this case, the intervals 10YS, 10KS, 10MS, and 10CS formed by the respective color patterns form intervals extending in a direction inclined at a predetermined angle (about 45 ° in this case) with respect to the belt conveyance direction.

  The color misregistration correction pattern according to the first embodiment formed as shown in FIG. 1 is used as a pattern for color misregistration correction in a tandem type color image forming apparatus using electrophotography technology. Compared with the conventional color misregistration correction pattern shown in FIG. 16, the shape is just inverted. In the color misregistration correction pattern 10 shown in FIG. 1, there are gaps between adjacent portions YKP, KMP, MCP, CYP, YKP, KMP, and MCP between the color patterns even when color misregistration occurs. In order not to occur, they are formed so as to overlap each other by a predetermined width. However, when the color misregistration width is large, it may be impossible to cope with the overlap of the predetermined width alone. Therefore, in this case, a plurality of color misregistration correction patterns of different sizes are used. First, a large color misregistration correction pattern is formed to roughly perform color misregistration correction, and then a small color misregistration correction pattern is formed. If the color misregistration correction accuracy is increased step by step so that fine color misregistration correction is performed, a color misregistration correction pattern in which each color pattern is overlapped by a predetermined width is sufficient.

  When the color misregistration correction pattern 10 shown in FIG. 1 is detected using a specular reflection sensor described later, intervals 10YR, 10KR, 10MR, 10CR, 10YS, 10KS, 10MS, 10CS having predetermined widths constituted by the respective color patterns are detected. Since the intermediate transfer belt is exposed only in the portion, regular reflection light can be detected. By cutting this detected waveform at a certain threshold level, the edge position of each color pattern can be accurately detected.

  Next, a color image forming apparatus capable of forming the color misregistration correction pattern shown in FIG. 1 will be described. 2 is a cross-sectional view illustrating a schematic configuration of the color copying machine according to the first embodiment, FIG. 3 is a D-direction arrow diagram illustrating the optical apparatus of FIG. 2, and FIG. FIG. 5 is a diagram for explaining the principle of a regular reflection light sensor that detects the surface state of the intermediate transfer belt of FIG. 2, FIG. 5 is a block diagram of components that perform color misregistration correction processing, and FIG. It is a functional block diagram explaining these.

  First, as shown in FIG. 2, an image forming apparatus 100 includes an exposure device 102 including optical elements such as a semiconductor laser and a polygon mirror, an image forming unit 112 including a photosensitive drum, a charging device, a developing device, and the like, A transfer unit 122 including a transfer belt and the like is included. The exposure apparatus 102 deflects a light beam emitted from a light source such as a semiconductor laser (not shown) by a polygon mirror 102P and makes it incident on an fθ lens 102KY and 102CM. As will be described later with reference to FIG. 3, light beams are generated in a number corresponding to each color of cyan (C), magenta (M), yellow (Y), and black (K), and the fθ lenses 102KY and 102CM are generated. After passing, it is reflected by the reflection mirrors 102Y, 102K, 102C, and 102M.

  The WTL lens 102d shapes the light beam, then deflects the light beam toward the reflection mirror 102e, and irradiates the photosensitive drum 108a with the light beam as a light beam L used for exposure. Similarly, the other light-sensitive drums 104a, 106a, and 110a are irradiated with the light beam L in an image form. The irradiation of the light beam L onto the photosensitive drums 104a, 106a, 108a, and 110a is performed using a plurality of optical elements as described above, so that the timing is synchronized in the main scanning direction and the sub-scanning direction. ing. Hereinafter, the main scanning direction is defined as the light beam scanning direction, and the sub-scanning direction is a direction orthogonal to the main scanning direction. In many image forming apparatuses 100, the photosensitive drums 104a, 106a, 108a, It is defined as the rotating direction of 110a.

  Each of the photosensitive drums 104a, 106a, 108a, and 110a includes a photoconductive layer including at least a charge generation layer and a charge transport layer on a conductive drum such as aluminum. The photoconductive layer is disposed corresponding to each of the photosensitive drums 104a, 106a, 108a, and 110a, and is charged with a surface charge by the chargers 104b, 106b, 108b, and 110b including a corotron, a scorotron, or a charging roller. Is granted.

  The electrostatic charges imparted on the photosensitive drums 104a, 106a, 108a, 110a by the respective chargers 104b, 106b, 108b, 110b are imagewise exposed by the light beam L to form an electrostatic latent image. The electrostatic latent images formed on the photoconductive drums 104a, 106a, 108a, and 110a are developed by the developing devices 104c, 106c, 108c, and 110c including a developing sleeve, a developer supplying roller, a regulating blade, and the like. Is formed.

  The developer images carried on the photosensitive drums 104a, 106a, 108a, and 110a are transferred onto the intermediate transfer belt 114 that moves in the direction of arrow E by the conveying rollers 114a, 114b, and 114c. The intermediate transfer belt 114 is transported to the secondary transfer unit while carrying K, Y, C, and M developers. The secondary transfer unit includes a secondary transfer belt 118 and conveying rollers 118a and 118b. The secondary transfer belt 118 is conveyed in the direction of arrow F by the conveyance rollers 118a and 118b. A transfer member 124 such as high-quality paper or a plastic sheet is supplied to the secondary transfer unit from an image receiving material storage unit 128 such as a paper feed cassette by a conveying roller 126.

  The secondary transfer unit applies a secondary transfer bias to transfer the multicolor developer image carried on the intermediate transfer belt 114 to a transfer member 124 held by suction on the secondary transfer belt 118. The transfer member 124 is supplied to the fixing device 120 along with the conveyance of the secondary transfer belt 118. The fixing device 120 includes a fixing member 130 such as a fixing roller including silicone rubber, fluorine rubber, and the like, pressurizes and heats the transfer member 124 and the multicolor developer image, and forms an image forming apparatus 100 as a printed matter 132. To the outside. After the multicolor developer image is transferred, the transfer belt 114 is supplied to the next image forming process after the transfer residual developer is removed by the cleaning unit 116 including a cleaning blade.

  A detection sensor that is a regular reflection light sensor is used to detect a color misregistration correction pattern formed on the intermediate transfer belt 114 near the end point in the main scanning direction of each of the photosensitive drums 104a, 106a, 108a, and 110a. 115a-c are installed. Based on the detection result of the color misregistration correction pattern, various misregistration amounts (skew, main / sub resist, magnification) of each color with respect to the reference color are calculated, and color misregistration correction is performed.

  Next, an exposure apparatus that is an optical unit will be described with reference to FIG. FIG. 3 is a view of the exposure apparatus 102 of FIG. 2 as viewed from the D direction. Light beams from LD (laser diode) units 19K and 19C pass through cylinder lenses 20K and 20C, respectively, and are incident on the lower surface of the polygon mirror 102P by the reflection mirrors 21K and 21C, and the polygon mirror 102P rotates in the direction of the arrow. To deflect the light beam, pass through the fθ lenses 102KY and 102CM, and are folded back by the first mirrors 102K and 102M.

  On the other hand, the light beams from the LD units 19Y and 19M pass through the cylinder lenses 20Y and 20M, enter the upper surface of the polygon mirror 102P, and the polygon mirror 102P rotates to deflect the light beam, and the fθ lenses 102KY and 102CM. And is folded back by the first mirrors 102Y and 102C.

  Cylinder mirrors 25KY and 25CM and sensors 26KY and 26CM are provided on the upstream side from the writing position in the main scanning direction, and the light beams that pass through the fθ lenses 102KY and 102CM are reflected and condensed by the cylinder mirrors 25KY and 25CM. It is configured to be incident on 26KY, 26CM. These sensors 26KY and 26CM are synchronization detection sensors for synchronizing in the main scanning direction. Further, similarly to the upstream side described above, cylinder mirrors 27KY and 27CM and sensors 28KY and 28CM are provided on the downstream side of the image region in the main scanning direction, and the light beam that has passed through the fθ lenses 102KY and 102CM is provided in the cylinder mirror. The light is reflected and collected by 27KY and 27CM and is incident on the sensor 28KY and the sensor 28CM.

  In the light beams from the LD units 19K and 19Y, the common cylinder mirror 25KY and sensor 26KY are used on the writing side, and the common cylinder mirror 27KY and sensor 28KY are used on the end side. The same applies to the LD unit 19C and the LD unit 19M. Since light beams of two colors are incident on the same sensor, the timing at which each light beam is incident on each sensor is changed by changing the incident angles of the polygon mirrors 102P for the light beams of the respective colors. It is output in series as a pulse train. As can be seen from FIG. 3, black (K) and yellow (Y), and cyan (C) and magenta (M) are scanned in opposite directions. Each color beam passes through the two beam detection sensors, and the passing time interval of each of the two sensors is measured by counting with a pixel clock or the like, and the count value and a preset reference count are measured. The writing image frequency is changed so that the values coincide with each other, and the magnification is corrected (magnification correction using the two-point synchronization method).

  If a color misregistration correction pattern is formed on the intermediate transfer belt 114, and detection and correction are performed, it takes time, and therefore cannot be performed frequently. During continuous printing or the like, the change in magnification becomes rapid due to the temperature rise of the fθ lens in the exposure apparatus 102 in particular. Therefore, a two-point synchronous magnification correction technique that can be executed in a short time is essential. This is especially true when the material of the fθ lens is plastic or the like, since the temperature rises rapidly. Because of this background, magnification correction is performed by a two-point synchronization method.

  Further, the detection sensors 115a to 115c, which are specular reflection light sensors provided near the intermediate transfer belt 114 of the color image forming apparatus 100 of FIG. 1, are configured as shown in FIG. The surface of the intermediate transfer belt 114 is detected by receiving light emitted toward the light 114 at the light receiving unit 31. The surface of the intermediate transfer belt 114 is regularly reflected and received by the light receiving unit 31, but diffusely reflected light that has been diffusely reflected is received by the surface of the color misregistration correction pattern 10 formed of a toner pattern. The state of the color misregistration correction pattern 10 can be detected by processing the waveform detected by the light receiving unit 31. The scratch 114a on the intermediate transfer belt 114 shown in FIG. 4 may be erroneously detected as a toner pattern because the light from the regular reflection light sensor becomes diffuse reflection light.

  However, since the color misregistration correction pattern 10 of the first embodiment has a pattern shape that covers the surface of the intermediate transfer belt 114 as much as possible as shown in FIG. 1, the intermediate transfer belt 114 shown in FIG. Even if there is a scratch (similar to foreign matter and unevenness) 114a on the surface, the color misregistration correction pattern 10 can be formed thereon to prevent erroneous detection.

  Next, detection data processing will be described with reference to FIG. Signals obtained from the light receiving units 31 of the detection sensors 115a to 115c in FIG. 5 are amplified by the amplifying unit 32, and only the signal component of the line detection is passed by the filter 33, and the A / D conversion unit 34 converts the signal from analog data. Converted to digital data. The data sampling process is controlled by the sampling control unit 35, and the sampled data is stored in the FIFO memory 36. After the detection of the set of color misregistration correction patterns is completed, the data stored in the FIFO memory 36 is loaded to the CPU 39 and the RAM 41 by the data bus 38 via the I / O port 37. By performing predetermined arithmetic processing, the above-described various color misregistration amounts are obtained. The ROM 40 stores various programs for controlling the color misregistration correction apparatus and the image forming apparatus, in addition to the above-described programs for calculating the various color misregistration amounts. Further, the CPU 39 monitors the detection signal from the light receiving unit 31 at an appropriate timing, and the light emission amount control unit 42 ensures that even if the intermediate transfer belt 114 and the light emitting unit 30 are deteriorated or the like is detected. The light emission amount is controlled, and the level of the light reception signal from the light receiving unit 31 is controlled to be always constant. As described above, the CPU 39 and the ROM 40 function as a control unit that controls the operation of the entire image forming apparatus.

  FIG. 6 shows functional blocks in the CPU 39 of FIG. As shown in FIG. 6, the CPU 39 includes a sampling unit 391 as a sampling unit that performs sampling control, a pattern position detection unit 392 as a pattern position detection unit that detects the position of each color pattern of the color misregistration correction pattern 10, and various calculations. A calculation unit 393 serving as a calculation unit that performs processing, a detection result discarding unit 394 serving as a detection result discarding unit that discards data detected when an appropriate detection result described later is not obtained, and the like are included. The calculation unit 393 includes a color shift amount calculating unit that calculates the color shift amount by comparing the position of each detected color pattern with the reference position, and color shift based on the calculated color shift amount of each color pattern. A function of color misregistration correction amount calculation means for calculating a correction amount is provided.

  FIG. 7 is a diagram illustrating an example of forming a color misregistration correction pattern formed on the intermediate transfer belt in the first embodiment, and FIG. 8 illustrates a state in which a scratch on the belt is exposed at the same color pattern interval. FIG. 9 is a flowchart for explaining the color misregistration correction processing according to the first embodiment. As shown in FIG. 7, in the first embodiment, the set of color misregistration correction patterns shown in FIG. 1 obtained by inverting the conventional color misregistration correction pattern shown in FIG. Three rows are formed in parallel in the conveyance direction of the intermediate transfer belt, and eight sets are further formed in the belt conveyance direction, although not shown. The detection sensors 115a to 115c are installed at positions for detecting color misregistration correction patterns formed in parallel in three rows on the intermediate transfer belt. For this reason, the sensor outputs of the detection sensors 115a to 115c detect specularly reflected light at intervals between the color patterns of the color misregistration correction pattern, so that a sensor output waveform as shown in the upper part of FIG. 7 can be detected. .

  However, although the probability is very small, as shown in FIG. 8, if an occasional scratch (foreign matter or unevenness of the belt) 114 a is included in the interval portion of each color pattern of the color misregistration correction pattern, the sensor output A waveform whose output waveform is different from the normal interval is detected. FIG. 8 shows a case where there is a long and narrow scratch 114a in a direction orthogonal to the belt conveyance direction. Since the diffused light is generated at the portion of the scratch 114a, the sensor output is lowered and the output waveform peak is divided into two. In the first embodiment, even in such a case, erroneous detection can be prevented by performing the processing described later.

  Therefore, the operation of the color misregistration correction process in the first embodiment will be described with reference to FIG. The color misregistration correction process is performed so that the color misregistration amount is always within a predetermined range by performing, for example, when the power is turned on, when the environment such as temperature changes, or when a predetermined number of sheets are printed. Can do. Of course, the timing is not necessarily limited, and the user can arbitrarily execute the timing.

  First, when the color misregistration correction process is started, a color misregistration correction pattern as shown in FIG. 7 in which a plurality of colors are arranged on the intermediate transfer belt 114 is formed by the image forming unit 112 in FIG. 2 (step S100). This is detected by the detection sensors 115a to 115c (step S101). Detection signals output from the light receiving units 31 of the detection sensors 115a to 115c are amplified by the amplifying unit 32 in FIG. 5, converted into digital signals by the A / D conversion unit 34 via the filter 33, and the sampling control unit 35. Is sampled (step S102). The sampling waveform is temporarily stored in the FIFO memory 36 and then stored in the RAM 41 via the I / O port 37. The pattern position detection unit 392 of the CPU 39 detects the edge of each color pattern using a predetermined threshold level. (Step S103), it is determined whether or not the detected edge interval of each color pattern is a predetermined interval (Step S104).

  Here, as shown in FIG. 8, if the edge interval of each color pattern is a predetermined interval (a), the CPU 39 determines that the interval is appropriate (YES in step S104), and in step S105, determines each color from the intermediate position of the edge. The position of the pattern is calculated and stored in the RAM 41.

  Subsequently, the CPU 39 compares the detected position of each color pattern with the normal reference position of each color pattern stored in the ROM 40 or the like to calculate various color misregistration amounts (step S106). Based on the calculated color misregistration amount, various color misregistration correction amounts are calculated and stored in the RAM 41 (step S107).

  The various color misregistration correction amounts obtained in this way are used as parameters for adjusting each section related to the color misregistration correction of the color image forming apparatus, and the color misregistration correction amount is adjusted automatically or manually to thereby obtain a highly accurate color. Deviation correction can be performed (step S108).

  In step S104, if the edge interval of each color pattern shown in FIG. 8 is not a predetermined interval, for example, if it is less than the predetermined interval (b), the CPU 39 can detect an appropriate interval based on scratches, foreign matter, and belt irregularities. It is determined that it is not present (NO in step S104), and the detection result discarding unit 394 of the CPU 39 discards the detection result (step S109). At this time, when an appropriate interval cannot be detected by a part of one set, various treatments can be considered. For example, (1) when an appropriate interval cannot be detected at one interval, all detection data of all the formed patterns are discarded, and (2) only a set of patterns for which an appropriate interval cannot be detected Only when the detection data is discarded and color misregistration correction is performed with the remaining detection data, and (3) it is valid until the set where the proper interval cannot be detected reaches a certain percentage of the whole, and only when it exceeds A case where all the detected data is discarded can be considered. This is only an example, and it is of course possible to employ other methods.

  As described above, according to the first embodiment, the color image forming apparatus 100 forms the color misregistration correction pattern shown in FIG. 1 or 7 on the intermediate transfer belt, and performs color misregistration correction processing using the pattern. Therefore, even if there are scratches, foreign matter, or surface irregularities on the intermediate transfer belt, it is possible to greatly reduce the probability of being affected by them, and if there are scratches, foreign matters, or irregularities on the surface of the color pattern, Even if the image is exposed, it is possible to easily determine whether or not the data is appropriate by checking the interval width, so that highly accurate color misregistration correction can be easily performed in a short time. In particular, in the first embodiment, since only the regular reflection light sensor is used as the detection sensor, it is not necessary to use two of the regular reflection light sensor and the diffuse reflection light sensor as shown in Patent Document 2, Cost can be further reduced. Further, the color misregistration correction pattern 10 according to the first embodiment can detect all pattern positions of Y, K, M, and C with only one set of patterns as shown in FIG. Color misregistration correction can be performed with only a set of patterns. However, in the conventional correction pattern shown in FIG. 17, the position of black (K) cannot be detected by only one set, and therefore, it is necessary to form a plurality of sets of patterns, which requires extra toner consumption.

(Second Embodiment)
A feature of the second embodiment is that a color misregistration correction pattern can be selected according to the state of the intermediate transfer belt so that the toner consumption can be suppressed as much as possible.

  FIG. 10 is a diagram showing a color misregistration correction pattern used in the second embodiment, and FIG. 11 is a waveform diagram for explaining a threshold level settable range in the second embodiment. FIG. 13 is a diagram for explaining a relationship between detection data of each color pattern and details of color misregistration correction, FIG. 13 is a diagram illustrating an example of forming a conventional color misregistration correction pattern, and FIG. 14 is a diagram illustrating a second embodiment. 15 is a flowchart for explaining the operation of the color misregistration correction process according to the embodiment, and FIG. 15 is a pattern edge portion when the drawing resolution of the color misregistration correction pattern is changed by enabling the selection of the light source used in the exposure apparatus. FIG.

  In the second embodiment, the image forming unit 112 in FIG. 2 performs color misregistration correction including a color misregistration correction pattern according to the present invention in which a plurality of color patterns as shown in FIG. Both patterns can be selectively formed. As shown in FIG. 10, it can be seen that the present invention and the conventional color misregistration correction pattern are just inverted patterns, and their sensor outputs are also in opposite phases. For this reason, depending on how the threshold level is set, a common threshold level can be used, and any pattern can be detected only by the regular reflection light sensor. Can be processed using the same.

  With respect to the settable range of the threshold level, as shown in FIG. 11, since the edge of the pattern is detected by the regular reflection light sensor, the settable range of the threshold level can be very wide. When comparing with the sensor output waveform shown in FIG. 18 detected using both the regular reflection light sensor and the diffuse reflection light sensor in FIG. For this reason, as shown in FIG. 11, even if electrical noise is on the sensor output waveform depending on how the threshold level is set, there is an advantage that this influence can be eliminated. In particular, the second embodiment is a case of switching to the conventional color misregistration correction pattern, but as shown in FIG. 10 and FIG. 11, the setting range of the threshold level can be wide. It is.

  In the second embodiment, the pattern of the present invention and the conventional pattern are completely different, but the processing after detecting the edge of each color pattern is the same, so the conventional pattern of FIG. 12 is used. The calculation of various color misregistration amounts will be described. Here, drawing is performed using four colors Y, K, M, and C, and the pattern is read by a regular reflection light sensor. In the regular reflection light sensor, the pattern time interval is measured at a constant sampling interval. The calculation unit 393 of the CPU 39 can acquire the pattern distance by converting the time into the distance. Using such a method, the color misregistration amount can be calculated by measuring the length between the horizontal line pattern and the diagonal line pattern of the same color shown in FIG. 12 and comparing the lengths. it can. For example, to calculate the amount of color misregistration in the sub-scanning direction (belt conveyance direction), a horizontal line pattern is used, and the pattern interval (y1, m1, c1) between black (K) as the reference color and the target color is measured, It can be calculated by comparing with an ideal interval (reference interval).

  On the other hand, when calculating the color misregistration amount in the main scanning direction, a horizontal line pattern and an oblique line pattern are used. The interval (y2, k2, m2, c2) between the horizontal line pattern and the diagonal line pattern of each color is measured. For the measured interval, the difference (y2-k2) in which the difference between black (K) as the reference color and yellow (Y) as the non-reference color is calculated is the color shift amount in the main scanning direction (45 for the oblique pattern). (Because it has an inclination of °). In this way, the amount of color misregistration in the sub-scanning direction and main scanning direction can be acquired.

  In addition, each component can be detected by using the detection sensors 115a to 115c having different main scanning positions. For example, if it is a skew component, it can be acquired by calculating the difference in the amount of color misregistration in the sub-scanning direction detected by the detection sensors 115a and 115c shown in FIG. 13, and 115a and 115b, 115b and 115c, By calculating the difference in the amount of color misregistration in the respective main scanning directions, the magnification error deviation can be obtained. In this way, the obtained various color misregistration amounts can be converted into the correction format of each device, and color misregistration correction can be performed. The case of FIG. 13 is the same as that of FIG. 7, and the conventional single-color pattern is formed on the intermediate transfer belt 114 as one set of four horizontal lines and four diagonal lines of each color, and eight sets of these sets are formed. To. By determining the correction amount from the result of calculating the average of these detection results, it is possible to form a high-quality image with little positional deviation in each color pattern. By forming these eight sets of Y, K, M, and C horizontal line patterns and diagonal line patterns, respectively, and detecting them using the sensors 115a, 115b, and 115c arranged in the main scanning direction, the reference color black It is possible to measure skew, sub-scanning registration deviation, main-scanning registration deviation, and main-scanning magnification error with respect to (K). The calculation unit 393 of the CPU 39 issues various displacement amounts, correction amount calculations, and correction execution instructions. The detected pattern is cleaned by the cleaning unit 116 shown in FIG.

  Next, the color misregistration correction operation according to the second embodiment will be described with reference to FIG. The flowchart shown in FIG. 14 is obtained by adding a color misregistration correction pattern switching operation to a part of the flowchart shown in FIG. As shown in FIG. 14, when the color misregistration correction operation is started, the state of the surface of the intermediate transfer belt is first detected by a sensor (step S200), and based on the detection result, there are scratches, foreign matter, irregularities, etc. on the belt surface. It is determined whether or not it has been detected (step S201).

  If the surface of the belt is good and no scratches, foreign matter, unevenness, or the like is detected (NO in step S201), the process proceeds to step S202, and the CPU 39 notifies the exposure apparatus 102 to the intermediate transfer belt 114. Then, switching control is performed so as to form a color misregistration correction pattern composed of the conventional single color pattern shown in FIG. The subsequent processing in step S101 and subsequent steps in FIG. 9 is the same as that described in the first embodiment, and will be omitted.

  If scratches, foreign matter, irregularities, or the like are detected on the belt surface in step S201 (YES in step S201), the process proceeds to step S100 in FIG. 9, and the CPU 39 sends the exposure apparatus 102 to the intermediate transfer belt 114. On the other hand, switching control is performed so as to form a color misregistration correction pattern comprising a plurality of color patterns of the present invention shown in FIG. Since the processing after step S100 is the same as that described in the first embodiment, a description thereof will be omitted.

  Further, in FIG. 15, it is possible to further improve the color misregistration correction accuracy by switching the exposure light source used by the exposure apparatus to one that can be reproduced with high resolution. For example, as shown in FIG. 15, when the edge portion of the color misregistration correction pattern is enlarged, the light source can be formed at a resolution of 4800 dpi by switching to a light source that can be reproduced at a higher resolution than when forming at 1200 dpi. As a result, a more accurate pattern shape can be reproduced, so that a more accurate color misregistration correction process can be performed.

  As described above, according to the second embodiment, before performing the color misregistration correction process, the surface state of the intermediate transfer belt is detected in advance using the sensor, and the multiple colors of the present invention are based on the detection result. Since it is possible to switch between forming a pattern and forming a conventional single color pattern, it is possible to easily perform highly accurate color misregistration correction in a short time while minimizing toner consumption. Also in the second embodiment, since only the regular reflection light sensor can be used as the detection sensor, there is no need to use two of the regular reflection light sensor and the diffuse reflection light sensor as shown in Patent Document 2. Similarly, the cost can be reduced.

  According to the second embodiment, the exposure light source of the exposure apparatus can be selected and switched to one that can be reproduced at a higher resolution, so that a more accurate color misregistration correction process can be performed.

  In each of the embodiments described above, the image forming apparatus of the present invention has been described as an example applied to a color copying machine. However, at least two functions of a copy function, a printer function, a scanner function, and a facsimile function are provided. The present invention can be applied to any example applied to a multifunction peripheral having the above-mentioned or any example applied to an image forming apparatus such as a printer or a facsimile machine.

DESCRIPTION OF SYMBOLS 10 Color misregistration correction pattern 30 Light emission part 31 Light reception part 32 Amplification part 33 Filter 34 A / D conversion part 35 Sampling control part 36 FIFO memory 37 I / O port 39 CPU
40 ROM
41 RAM
42 Light emission amount control unit 102 Exposure device 112 Image forming unit 114 Intermediate transfer belt (image carrier)
115a-c Detection sensor (regular reflection light sensor)
391 Sampling unit 392 Pattern position detection unit 393 Calculation unit 394 Detection result discarding unit

JP 2008-287153 A JP 2008-225163 A

Claims (7)

An image forming apparatus that forms a color image by superimposing a reference color and a plurality of non-reference color images,
Pattern forming means for forming a color misregistration correction pattern on the image carrier;
Pattern detecting means for detecting each color pattern formed by a reference color and a plurality of non-reference colors of the color misregistration correction pattern formed on the image carrier;
Sampling means for sampling the detection signal by the pattern detection means;
Pattern position detection means for detecting an edge of each color pattern by a sampling waveform by the sampling means and a predetermined threshold level, calculating an intermediate point from the edge, and detecting a position of each color pattern;
A color shift amount is calculated by comparing the position of each color pattern detected by the pattern position detection unit with a reference position, and a color shift correction amount is calculated based on the color shift amount;
Control means for controlling each part of the apparatus main body related to color misregistration based on the color misregistration correction amount calculated by the arithmetic means;
Color misregistration correction by controlling each part of the apparatus body by the control means ,
The color misregistration correction pattern is:
A color pattern of the same color is formed on each of the downstream side and the upstream side in the conveyance direction of the image carrier at a predetermined interval,
The color pattern is composed of the reference color and the plurality of non-reference colors, respectively, and the color patterns are arranged adjacent to each other along the conveyance direction of the image carrier,
A portion where the color patterns of the reference color and the plurality of non-reference colors are adjacent to each other is formed to overlap with a predetermined width with respect to the conveyance direction of the image carrier.
Image forming apparatus. The interval constituted by the same color pattern includes an interval extending in a direction orthogonal to the conveyance direction of the image carrier and the conveyance direction of the image carrier for each of the reference color and the plurality of non-reference colors. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus includes two types of an interval extending in a direction inclined with respect to a predetermined angle . The computing means is
A color misregistration amount calculating unit that calculates a color misregistration amount by comparing the position of each color pattern detected by the pattern position detecting unit with a reference position of each color pattern;
Color misregistration correction amount calculating means for calculating a color misregistration correction amount based on the color misregistration amount of each color pattern calculated by the color misregistration amount calculating means;
The image forming apparatus according to claim 1, further comprising: Pattern interval detection means for detecting whether the edge interval of each color pattern is a predetermined interval based on the edge of each color pattern detected by the pattern position detection means;
A detection result discarding unit that discards the detection result of each color pattern when the pattern interval detection unit detects that at least one interval of each color pattern is narrower than a predetermined interval;
The image forming apparatus according to claim 1, further comprising: The pattern forming means includes
A first of the color misregistration correction pattern, by inverting the color registration patterns of the first and the second of the color misregistration correction pattern to form a single color pattern in positions corresponding to the spacing of the respective color patterns It can be formed on the image carrier,
Surface state detecting means for detecting the surface state of the image carrier,
If scratches or foreign matter are detected on the surface of the image carrier before the image formation, the first color misregistration correction pattern is placed on the image carrier with respect to the pattern formation unit. And when the surface state detection means detects no scratches or foreign matter on the surface of the image carrier, the image carrier is provided with the second color misregistration correction pattern for the pattern formation means. Switching control means for performing switching control so as to form on the top,
The image forming apparatus according to claim 1, further comprising: It said patterning means, according to any one of claims 1 to 5, characterized in that to allow formation of the color misregistration correction pattern on the image bearing member by using a plurality of light sources selectively Image forming apparatus. A color misregistration correction method executed in an image forming apparatus,
The image forming apparatus includes a pattern forming unit, a pattern detection unit, a sampling unit, a pattern position detection unit, a calculation unit, and a control unit.
The pattern forming means forming a color misregistration correction pattern on the image carrier;
The pattern detecting means detecting each color pattern formed by a reference color and a plurality of non-reference colors of the color misregistration correction pattern formed on the image carrier;
The sampling means sampling the detection signal of the color misregistration correction pattern; and
The pattern position detecting means detects an edge of each color pattern based on a sampling waveform and a predetermined threshold level, calculates an intermediate point from the edge, and detects a position of each color pattern;
A step of calculating a color misregistration amount by comparing the position of each color pattern with a reference position, and calculating a color misregistration correction amount based on the color misregistration amount;
The control means controlling each part of the apparatus main body related to color misregistration based on the color misregistration correction amount;
Color correction by controlling each part of the apparatus body ,
The color misregistration correction pattern is:
A color pattern of the same color is formed on each of the downstream side and the upstream side in the conveyance direction of the image carrier at a predetermined interval,
The color pattern is composed of the reference color and the plurality of non-reference colors, respectively, and the color patterns are arranged adjacent to each other along the conveyance direction of the image carrier,
A portion where the color patterns of the reference color and the plurality of non-reference colors are adjacent to each other is formed to overlap with a predetermined width with respect to the conveyance direction of the image carrier.
Color misregistration correction method.

Images