JP2006078561A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus capable of correcting positional deviation on a pixel level in a main scanning direction with inexpensive constitution in a short time. <P>SOLUTION: The color image forming apparatus is equipped with an image forming control means which prescribes corresponding information on positional deviation in a main scanning direction by collating the present temperature of an image forming means measured by a temperature measuring means with a temperature/main scanning direction positional deviation information storage means before starting color image forming operation by the image forming means, and sets information on write-in clock generation timing based on the prescribed information on the positional deviation in the main scanning direction. Thus, the correction of the positional deviation optimum for the present temperature in the color image forming operation by the image forming means is realized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a color image forming apparatus applicable to a copying machine, a digital multifunction peripheral, a facsimile apparatus, a printer apparatus, and the like, and in particular, image data of each color component constituting color image data to be formed is converted to each pixel in the main scanning direction. The electrostatic latent image is generated by irradiating the photosensitive member corresponding to each color component by modulating the intensity of the laser light in synchronization with the write clock generated based on the write clock generation timing information that defines the write timing of The present invention relates to a color image forming apparatus including an image forming unit that forms an electrostatic latent image into a toner image by a developing unit corresponding to each color component and superimposes the toner image on a transfer medium.

  In a conventional color image forming apparatus, single-color image data corresponding to each color component constituting the color image data to be formed is transported (transferred) in a transfer medium, that is, a type in which an image is directly transferred to recording paper. In an apparatus of a type in which an image once formed on a transfer belt is transferred to a recording sheet on a conveyance (secondary transfer) belt, an image forming unit that forms a color image by transferring the images on the transfer belt in a superimposed manner is provided. .

  In that case, if the writing start timing in each of the main scanning direction and the sub-scanning direction in the electrophotographic image forming unit corresponding to each color component constituting the image forming unit is fixed, each electrophotographic image forming unit corresponding to each color The image of each color component superimposed on the transfer medium is shifted from each other due to an attachment error at the manufacturing stage of the relative arrangement relationship with the transfer medium or an error due to a change with time.

  Therefore, in the color image forming apparatus, prior to the actual printing of the image to be printed, the image formation control unit performs a positional deviation correction process, and finely adjusts the writing start timing in the electrophotographic image forming unit corresponding to each color component. Like to do.

  Specifically, a misregistration detection mark for each color is formed on the photosensitive member at a timing that is regarded as a writing timing at which no misregistration (color misregistration) currently occurs on the image formation control means side, and transferred onto a transfer medium. The mark formed by the transfer is read by a reflection type or transmission type optical sensor, and the actual reading timing of each color misregistration detection mark is compared with the reading timing theoretically predicted from the writing timing. A misregistration amount is calculated from the misregistration, and the writing timing is adjusted by an amount corresponding to the misregistration amount, so that no misregistration occurs in actual color image formation.

  However, in such a write timing adjustment form by forming / reading a position shift detection mark, even if the write start timing shift in the main scanning direction and the sub-scanning direction can be corrected, the pixel level in the main scanning direction can be corrected. The deviation of the recording position (main scanning error deviation) could not be corrected.

  The main scanning error deviation is caused by the distortion of the optical system through which the recording laser beam passes, specifically, the distortion of the fθ lens. This is due to deviation from the ideal equal interval.

  In principle, the main scanning error deviation is measured in units of pixels so that the positional deviation amount due to the distortion of the actual optical system is measured every time the color image forming operation is performed and the measured positional deviation amount is adapted. This can be dealt with by changing the timing of the write clock in units of pixels.

  However, in such a method by adjusting the timing of the write clock in units of pixels, the correction accuracy is lowered when the number of sensors in the main scanning direction is small, and conversely, increasing the number of sensors causes an increase in apparatus cost. There was a point.

Patent Document 1 can be cited as a known technique relating to correction of main scanning error deviation.
JP 2002-091112 A

  However, even if the technique described in Patent Document 1 can correct the main scanning error deviation, it is necessary to measure the positional deviation amount for the correction before the correction, and it takes time to correct the main scanning error deviation. As a result, there is a problem that the image forming operation is hindered.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a color image forming apparatus capable of correcting a pixel level positional shift in the main scanning direction in a short time with a low-cost configuration.

  The color image forming apparatus according to claim 1 generates image data of each color component constituting the color image data to be formed based on write clock generation timing information that defines a write timing of each pixel in the main scanning direction. The electrostatic latent image is modulated by modulating the intensity of the laser light in synchronization with the writing clock to be irradiated onto the photosensitive member corresponding to each color component to form an electrostatic latent image, and the electrostatic latent image is developed by a developing unit corresponding to each color component. In a color image forming apparatus having an image forming means for forming a toner image and superimposing the toner image on a transfer medium, the temperature of the image forming means is changed in advance and collected for each temperature on the transfer medium. Temperature / main scanning direction positional deviation amount information for storing main scanning direction positional deviation amount information, which is information about the pixel level positional deviation amount of the formed color component image in the main scanning direction. Memory means, temperature measuring means for measuring the temperature of the image forming means, and the current temperature of the image forming means measured by the temperature measuring means prior to the start of a color image forming operation by the image forming means. / The main scanning direction positional deviation amount information storage means is collated to identify the corresponding main scanning direction positional deviation amount information, and the write clock generation timing information is set based on the identified main scanning direction positional deviation amount information. A color image forming apparatus comprising an image forming control unit, and capable of correcting a misalignment optimum for a current temperature in a color image forming operation in the image forming unit.

  The color image forming apparatus according to claim 2 is the color image forming apparatus according to claim 1, wherein the image forming control unit performs measurement by the temperature measuring unit prior to the start of the color image forming operation by the image forming unit. The corresponding current temperature of the image forming means is compared with the temperature / main scanning direction positional deviation amount information storage means to identify corresponding main scanning direction positional deviation amount information, and the identified main scanning direction positional deviation amount information The write clock generation timing information is set on the basis of the above, and a misregistration inspection pattern is formed on the transfer medium by the image forming unit and read by a predetermined reading unit, so that the entire line in the main scanning direction is globally displayed. A positional shift amount is acquired, and the write clock generation timing information is corrected based on the acquired positional shift amount. To.

  The color image forming apparatus according to claim 3 is the color image forming apparatus according to claim 1, wherein the image forming control unit measures the temperature by the temperature measuring unit prior to the start of the color image forming operation by the image forming unit. The corresponding current temperature of the image forming means is compared with the temperature / main scanning direction positional deviation amount information storage means to identify corresponding main scanning direction positional deviation amount information, and the identified main scanning direction positional deviation amount information The write clock generation timing information is set on the basis of the above, and a misalignment inspection pattern is formed on the transfer medium by the image forming unit and read by a predetermined reading unit, so that the entire line in the main scanning direction is A correct misalignment amount, correct the write clock generation timing information based on the acquired misalignment amount, and Modification by the formation and reading of the test pattern is characterized by is performed only when a predetermined instruction operation input.

  The color image forming apparatus according to claim 4 is the color image forming apparatus according to claim 1, wherein the image forming control unit measures the temperature by the temperature measuring unit prior to the start of the color image forming operation by the image forming unit. The corresponding current temperature of the image forming means is compared with the temperature / main scanning direction positional deviation amount information storage means to identify corresponding main scanning direction positional deviation amount information, and the identified main scanning direction positional deviation amount information The write clock generation timing information is set on the basis of the above, and a misalignment inspection pattern is formed on the transfer medium by the image forming unit and read by a predetermined reading unit, so that the entire line in the main scanning direction is A correct misalignment amount, correct the write clock generation timing information based on the acquired misalignment amount, and In the correction by the formation / reading of the inspection pattern, the difference between the temperature measured by the temperature measuring unit at the time of the previous correction and the temperature measured by the temperature measuring unit at the time of the current color image forming operation is a predetermined temperature difference or more. It is performed only in certain cases.

  The color image forming apparatus according to claim 5 is the color image forming apparatus according to claim 1, wherein the image forming control unit performs measurement by the temperature measuring unit prior to the start of the color image forming operation by the image forming unit. The corresponding current temperature of the image forming means is compared with the temperature / main scanning direction positional deviation amount information storage means to identify corresponding main scanning direction positional deviation amount information, and the identified main scanning direction positional deviation amount information The write clock generation timing information is set on the basis of the above, and a misregistration inspection pattern is formed on the transfer medium by the image forming unit and read by a predetermined reading unit, so that the entire line in the main scanning direction is globally displayed. Acquiring a positional deviation amount, correcting the write clock generation timing information based on the acquired positional deviation amount, and obtaining the acquired Characterized in that it is intended to correct the main scanning direction positional shift amount information to the current temperature in the temperature / main scanning direction positional shift amount information storage unit of the image forming means on the basis of the location shift amount.

  The color image forming apparatus according to claim 6 is the color image forming apparatus according to any one of claims 1 to 5, wherein the image forming unit is stored in the temperature / main scanning direction positional deviation amount information storage unit. In the main scanning direction positional deviation amount information collected for each temperature, a predetermined positional deviation detection pattern is formed on the transfer medium by the image forming unit, and is transferred to a recording paper and output. It is collected by reading.

  The color image forming apparatus according to claim 7 is the color image forming apparatus according to any one of claims 1 to 5, wherein the image forming unit is stored in the temperature / main scanning direction positional deviation amount information storage unit. The main-scanning-direction positional deviation amount information collected for each temperature is collected by directly reading laser light deflected in the main-scanning direction corresponding to a predetermined misregistration detection pattern. And

  The color image forming apparatus according to claim 8 is the color image forming apparatus according to claim 1, wherein the image forming control unit performs measurement by the temperature measuring unit prior to the start of the color image forming operation by the image forming unit. The corresponding current temperature of the image forming means is compared with the temperature / main scanning direction positional deviation amount information storage means to identify corresponding main scanning direction positional deviation amount information, and the identified main scanning direction positional deviation amount information The write clock generation timing information is set on the basis of the temperature of the temperature measured by the temperature measuring unit at the previous setting and the temperature measured by the temperature measuring unit during the current color image forming operation. This is performed only when the difference is equal to or greater than a predetermined temperature difference.

  The color image forming apparatus according to claim 9 is the color image forming apparatus according to claim 1, wherein the image formation control unit performs the color image formation continuously for each page or each document. The current temperature of the image forming unit measured by the temperature measuring unit prior to the start of the color image forming operation by the image forming unit is checked against the temperature / main scanning direction positional deviation amount information storing unit. The main scanning direction positional deviation amount information is specified, and the write clock generation timing information is set based on the specified main scanning direction positional deviation amount information.

  The color image forming apparatus according to claim 10 is the color image forming apparatus according to claim 1, wherein the deflecting means for irradiating the photosensitive member corresponding to each color component with a laser beam is a polygon motor. To do.

  The color image forming apparatus according to claim 11 is the color image forming apparatus according to claim 1, wherein the temperature measuring unit measures a temperature or a temperature distribution of an fθ lens constituting the image forming unit. It is characterized by that.

  A color image forming apparatus according to a twelfth aspect is the color image forming apparatus according to the first aspect, wherein the temperature measuring means is a thermocouple.

  According to the first aspect of the present invention, the main image of each color component image superimposed on the transfer medium that changes due to distortion or the like according to a temperature change of a lens or a mirror constituting the image forming unit. Since the amount of displacement of the pixel level in the scanning direction is optimally corrected to the temperature at which the image forming unit starts the color image forming operation, the pixel level in the main scanning direction is not affected by the temperature change of the image forming unit. There is an effect that it is possible to obtain a good superimposed image in which color misregistration is corrected. Compared with the case where a misregistration inspection pattern is formed on the transfer medium before the color image forming operation is started and the misregistration amount of each color component is confirmed and corrected, the time required for the correction work can be greatly reduced. In particular, there is an advantage that the color image forming speed can be improved.

  According to the second aspect of the present invention, the local misregistration amount at the pixel level in the main scanning direction is determined by the global misregistration amount of the entire line in the main scanning direction acquired by forming and reading the misregistration inspection pattern. Since the write clock generation timing information set based on the main scanning direction positional deviation amount information, which is information, is corrected, the main scanning direction positional deviation amount information alone cannot be removed due to changes over time. It is also possible to correct the positional shift of each color component in the entire line in the scanning direction, and to obtain an effect that a good superimposed image can be obtained.

According to the third aspect of the present invention, the local misregistration amount at the pixel level in the main scanning direction is determined by the global misregistration amount of the entire line in the main scanning direction acquired by forming and reading the misregistration inspection pattern. Since the write clock generation timing information set based on the main scanning direction positional deviation amount information, which is information, is corrected, the main scanning direction positional deviation amount information alone cannot be removed due to changes over time. It is also possible to correct the positional shift of each color component in the entire line in the scanning direction, and to obtain an effect that a good superimposed image can be obtained.
In addition, the correction by forming / reading the misregistration inspection pattern in that case is performed only when there is an instruction operation input by the user, so that it is possible to minimize the formation / reading of the misregistration inspection pattern which requires time. As compared with the invention according to Item 2, an effect is obtained in which the color image forming speed can be substantially increased.

According to the fourth aspect of the present invention, the local misregistration amount of the pixel level in the main scanning direction is determined by the global misregistration amount of the entire line in the main scanning direction acquired by forming and reading the misregistration inspection pattern. Since the write clock generation timing information set based on the main scanning direction positional deviation amount information, which is information, is corrected, the main scanning direction positional deviation amount information alone cannot be removed due to changes over time. It is also possible to correct the positional shift of each color component in the entire line in the scanning direction, and to obtain an effect that a good superimposed image can be obtained.
In this case, the correction due to the formation / reading of the misregistration inspection pattern is considered to have a temperature difference greater than a predetermined temperature difference from the previous correction, that is, the misregistration amount is larger than the previous one. Since it is automatically performed only in some cases, it is possible to minimize the time-consuming formation / reading of the misregistration inspection pattern, and the color image forming speed can be substantially increased as compared with the invention according to claim 2. A possible effect is obtained.

  According to the fifth aspect of the present invention, the local misregistration amount of the pixel level in the main scanning direction is determined by the global misregistration amount of the entire line in the main scanning direction acquired by forming and reading the misregistration inspection pattern. Since the write clock generation timing information set based on the main scanning direction positional deviation amount information, which is information, is corrected, the main scanning direction positional deviation amount information alone cannot be removed due to changes over time. It is also possible to correct the positional shift of each color component in the entire line in the scanning direction, and to obtain an effect that a good superimposed image can be obtained. In addition, the main-scanning-direction positional deviation information corresponding to the temperature of the image forming means automatically determines the mode of the overall positional deviation amount of the entire line in the main-scanning direction obtained by forming / reading the positional deviation inspection pattern. Since the correction is made, it is possible to obtain an effect of enabling color image formation without a positional shift that offsets the influence of the change with time.

  According to the sixth aspect of the present invention, it is possible to easily collect the positional deviation amount information in the main scanning direction by printing the positional deviation detection pattern on a recording sheet and reading the pattern by a reading unit such as a scanner. The effect becomes.

  According to the seventh aspect of the invention, the laser beam deflected in the main scanning direction corresponding to a predetermined misregistration detection pattern is directly read, so that the main scanning direction misregistration amount information can be obtained without waste of recording paper. The effect that it can be easily collected is obtained.

  According to the eighth aspect of the present invention, there is an advantage that the write clock generation timing information is not reset unnecessarily when the temperature change is small, that is, when the change in the positional deviation amount due to the temperature change is small. is there.

  According to the ninth aspect of the present invention, when forming a color image continuously on a plurality of pages, or forming a color image on a plurality of documents composed of one or a plurality of pages, each page or each document Since writing can be performed with a write clock that is optimally corrected for misregistration at the current temperature of the image forming unit every time, there is no misregistration even if the temperature of the image forming unit changes during successive color image forming operations. An effect of enabling color image formation is obtained.

  According to the tenth aspect of the present invention, there is an effect that the invention of the first aspect can be applied to an apparatus using a polygon motor as a deflecting means.

  According to the eleventh aspect of the present invention, the optimum writing timing can be set for the temperature or temperature portion of the fθ lens, which has a large influence on the variation of the positional shift amount due to the temperature change. An effect of enabling image formation is obtained.

  According to the invention which concerns on Claim 12, the effect which becomes possible to apply a thermocouple as said temperature measurement means is acquired.

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

  FIG. 1 shows a system configuration including a color image forming apparatus 1 according to the best mode for carrying out the present invention.

  In FIG. 1, a color image forming apparatus 1 is connected to a PSTN 200 and receives color or monochrome document image data from a facsimile apparatus 201 or the like on the PSTN 200.

  The color image forming apparatus 1 can receive color and monochrome document image data from the G4 facsimile apparatus 31 on the ISDN 300 as long as it has a necessary interface and protocol function.

  The color image forming apparatus 1 is also connected to the LAN 100, and can receive color and monochrome document image data related to a print request from an information processing apparatus such as the PCs 101a, 101b, and 101c on the LAN 100.

  The LAN 100 is connected to the Internet 400 via the router device 102 which is a device that performs packet conversion. The color image forming apparatus 1 connected to the LAN 100 receives color or monochrome data from the personal computer 402 on the Internet 400 by e-mail. Received from the network facsimile apparatus 401 on the Internet 400, ITU-T recommendation T.3. 38, real-time network facsimile communication and ITU-T recommendation T.38. Color and monochrome document image data can be received by electronic mail type network facsimile communication conforming to 37.

  FIG. 2 shows a block configuration of the color image forming apparatus 1 according to the best mode for carrying out the present invention.

  In the figure, a CPU 2 is a central processing unit that controls each part of the apparatus, performs various data processing, and performs protocol control based on a control program written in the ROM 3 while using a RAM 4 as a work area. .

  The ROM 3 is a read-only memory that stores various data necessary for control such as a control program for the CPU 2 to control each part of the apparatus and font data corresponding to each character code.

  The RAM 4 is a random access memory used as a work area for the CPU 2 as described above.

  An EEPROM (electrically rewritable read-only memory) 5 is a memory for storing various information necessary for the operation of the apparatus and holding the stored contents even when the apparatus is turned off. Replacement with a backed up SRAM (static RAM) or a magnetic disk device is also possible.

  The clock circuit 6 always keeps track of the current date and time, and the CPU 2 can read the clock circuit 6 via the system bus 14 to know the current date and time (date and time).

  The operation display unit 7 is provided with various keys for accepting operation inputs from the user, and includes a display such as a liquid crystal display device, and displays an operation state of the device to be notified to the user and various messages. It is.

  The image reading unit 8 is for reading a set original and obtaining color or monochrome document image data.

  The image forming section 9 as image forming means is for forming and outputting color or monochrome image data on a recording sheet by electrophotography.

  The image processing unit 10 encodes and compresses raw image data and decodes / decodes the encoded compressed data, binarization process, scaling process, reduction / enlargement process, and image correction process. Various image processing relating to image data handled in the color image forming apparatus 1 such as additional processing of additional information such as character string information of transmission date / time and reception date / time is performed.

  The LAN communication control unit is a so-called NIC (Network Interface Card), and is connected to the LAN 100 so that various information can be exchanged via the LAN 100.

  The communication control unit 12 is connected to the PSTN 200 via the NCU unit 13 and controls communication with the counterpart communication terminal. The communication control unit 12 controls the NCU unit 13 to detect a ringing voltage pulse detected by the NCU unit 13, a DTMF signal, a tone signal, and a call at the time of transmission. Further, the communication control unit 12 has a modem, and demodulates reception data (modulated) received from the counterpart communication terminal, or conversely modulates and transmits transmission data at the time of transmission. . Specifically, ITU-T recommendation T.I. A low-speed modem function (V.21 modem) for exchanging G3 facsimile control signals based on G.30 and a high-speed modem function mainly for exchanging document image data. 17, V.R. 33, V.R. 34, V.R. 29, V.R. It has 27ter modem functions.

  The NCU unit 13 is connected to the PSTN 200, and closes the line and detects a call signal (ringing).

  The system bus 14 is a signal line composed of a data bus, an address bus, a control bus, an interrupt signal line, and the like for the above units to exchange data.

  FIG. 3 shows the contents stored in the EEPROM of the color image forming apparatus 1.

  In the figure, the EEPROM 5 stores in advance a temperature / main scanning direction positional deviation amount information correspondence table 5a as temperature / main scanning direction positional deviation amount information storage means.

  The table 5a stores information indicating the amount of positional deviation at the pixel level in the main scanning direction actually measured for each temperature by changing the temperature of the image forming unit 9 of the color image forming apparatus 1. .

Collection of positional deviation amount information in the main scanning direction for each temperature constituting the table 5a is performed by transferring a predetermined positional deviation detection pattern onto the recording paper by the image forming unit 9 at each temperature of the image forming unit 9. The output recording paper can be read as a special document by the image reading unit 8 serving as a reading unit, and the positional deviation amount at the pixel level in the main scanning direction can be detected.
In this case, for example, vertical lines in the sub-scanning direction formed at constant pixel intervals in the main scanning direction can be applied to the misregistration detection pattern. If there is no positional deviation, the interval between the vertical lines corresponding to each color component should be constant, and if it is not constant, the deviation of the interval is the amount of positional deviation at the pixel level. The collection takes time, but once collected, a write clock optimal for misregistration correction can be set in a short time only by measuring the temperature of the image forming unit 9 during the color image forming operation.

  Further, the collection of positional deviation amount information in the main scanning direction for each temperature constituting the table 5a is deflected in the main scanning direction corresponding to the predetermined positional deviation detection pattern at each temperature of the image forming unit 9. Laser light may be collected by directly reading it with an optical sensor such as a CCD. As a result, information can be collected more rapidly than in the case of transfer formation / reading on a recording sheet. In that case, the optical sensor may be set in the color image forming apparatus 1 only when information on the table 5a is collected, so that the apparatus cost can be reduced.

  FIG. 4 shows the contents stored in the RAM 4 of the color image forming apparatus 1.

  In the figure, the RAM 4 stores write clock generation timing information 4a. The information 4a is referred to for generating a write clock when the image forming unit 9 performs an image forming operation.

  FIG. 5 shows the configuration of the image forming unit 9 of the color image forming apparatus 1.

  In the figure, an image forming unit 9 is a so-called tandem type corresponding to a color image, and the one shown in the figure is a so-called direct transfer type, and is controlled by the image forming control unit 110 such as a recording paper. An image is directly transferred and formed on a recording medium.

  In the drawing, a transfer belt 151 as a transfer medium is wound around a driving roller 152 and a driven roller 153 and rotated counterclockwise in the drawing by a driving roller 152 driven to rotate by a motor (not shown).

  The transfer belt 151 includes photosensitive drums 102K, 102C, 102M, and 102Y as photosensitive members corresponding to color components of K (black), C (cyan), M (magenta), and Y (yellow). The upper surfaces of the transfer rollers 104K, 104C, 104M, and 104Y that are paired with the respective photosensitive drums move to the left in the figure while being sandwiched, and are inverted by the driving roller 152 to become the lower surfaces and to the right. It moves and reverses again by the driven roller to become the upper surface and repeats the movement to the left.

  On the other hand, an image of the color component x is written on the photosensitive drum 102x (x = K, C, M, or Y). That is, the surface of each photosensitive drum x is uniformly charged by a charger (not shown), and then the image content of the color component x is controlled by laser diode light scanning control corresponding to each color component from the optical scanning writing 101. The electrostatic latent image is formed by discharging the position corresponding to the electrostatic latent image, and the electrostatic latent image is developed (toner attached) by the developing device 103x to become a toner image x.

  The toner image x is transferred onto the transfer belt 151. In that case, the toner image x of each color component of CMYK is transferred onto the transfer belt 151 by shifting the writing timing of the optical scanning writing unit 101 to the photoconductor 102x with respect to the arrangement position of the photoconductor 102x with respect to the transfer belt 151. Is formed as a color superimposed image within a predetermined image recording range.

  Since the image forming unit 9 shown in FIG. 5 is a direct transfer method, the image forming unit 9 is directly transferred to a recording medium such as a recording sheet conveyed from the right side in the drawing by the conveying roller 106 and placed in close contact with the previous image recording range on the transfer belt 151. The toner image x written on each photosensitive drum 102x is transferred, thermally fixed by the fixing unit 107, and discharged.

  The optical scanning / writing unit 101 is controlled by the image formation control unit 110. The image formation control unit 110 receives the write clock generation timing information of FIG. 4 from the CPU 2 via the system bus 14 and generates the write clock generation timing for each pixel generated by itself, that is, the clock corresponding to each pixel. After setting the cycle, the image data is read in units of main scanning lines from the storage address of the image data to be formed on the RAM 4 notified from the CPU 2 via the system bus 14, and the light is synchronized with the set write clock. The output light from the laser diode unit x corresponding to each component x of the scanning / writing unit 101 is modulated, and an image of each color component x is written on each photosensitive drum 102x.

  At this time, the image forming control unit 110 determines the theoretical writing timing determined by the design positional relationship between the photosensitive drums 102x and the transfer belt 151 and the like, and sets the photosensitive members 102x, the transfer belt 151, and the optical scanning writing unit. It is necessary to perform correction so as not to cause color misalignment due to mutual mechanical errors of the optical system 101 or the like and fluctuations of these errors over time. Prior to the start of the forming operation, it can be realized by setting appropriate information as the write clock generation timing information of FIG.

  The light detection sensor 120 reads a color misregistration detection pattern formed on a transfer belt 151 as a transfer medium and detects a relative formation position relationship between patterns corresponding to each color component x. . The relative formation position relationship between the patterns actually formed on the transfer belt 151 and corresponding to each color component x detected by the light detection sensor 120 is a theoretically predicted relative to the current writing clock setting. Information on the amount of color misregistration currently occurring can be obtained from the deviation from the typical formation position relationship.

  As the light detection sensor 120, a CCD image sensor can be applied to read the color misregistration detection pattern in the same manner as the original image is read by the image reading unit 8, but the light beam from the laser diode is transferred to the transfer belt. It is possible to apply a simple configuration that detects the formation position of the color misregistration detection pattern by irradiating the surface 151 and receiving the reflected light by a photodiode. The detection result of the light detection sensor 120 is passed to the CPU 2 by the image formation control unit 110 via the system bus 14.

  The temperature sensor 130 serving as a temperature measuring unit detects the temperature in the image forming unit 9. The detection result of the temperature sensor 130 is passed to the CPU 2 by the image formation control unit 110 via the system bus 14. A thermocouple can be applied as the temperature sensor 130. The temperature sensor is preferably arranged in a state where it is thermally coupled to the fθ lens 205KC and / or 205YM in the optical scanning writing unit shown in FIG. This is because a considerable portion of the local positional deviation at the pixel level in the main scanning direction due to the temperature change is caused by distortion due to the temperature change of the fθ lens 205KC or / and 205YM. In that case, the average of the temperatures of the fθ lenses 205KC and 205YM may be detected as the temperature of the image forming unit 9, or the temperatures of the fθ lenses 205KC and 205YM may be detected independently of each other. However, in that case, the table 5a in FIG. 3 needs to be configured as the correspondence of the positional deviation amount information in the main scanning direction to the combination of the temperatures of the fθ lenses 205KC and 205YM. Further, the temperature sensor 130 is multi-pointed to measure the temperature distribution of the fθ lens 205KC or / 205YM, and in the table 5a, the positional deviation amount information in the main scanning direction is set to correspond to the temperature distribution. Also good. In that case, it is possible to perform a finer positional deviation correction.

  FIG. 6 shows a configuration different from that of FIG. 5 of the image forming unit 9 of the color image forming apparatus 1.

  The configuration example shown in FIG. 6 is a so-called indirect transfer system, and is different from the direct transfer system shown in FIG. 5 in that a color superimposed image is directly transferred and formed within the image recording range of the transfer belt 151. The superimposed color image is conveyed from the lower side to the upper side in the drawing by the conveyance roller 108 and is re-transferred onto the recording paper that is nipped between the secondary transfer roller 160 and the driving roller 152 and rotated, and the fixing unit 109. Thus, it is thermally fixed and discharged, and other configurations and operations are the same as those of the direct transfer system shown in FIG.

  FIG. 7 shows a misregistration inspection pattern formed on the transfer belt by the image forming unit 9 having the configuration shown in FIG. 5 or FIG.

  In the figure, on the transfer belt 151, strip-like patterns corresponding to the respective color components of KCMY serving as a color misregistration detection pattern on the left end, center, and right side of the main scanning direction (perpendicular to the conveyance (sub-scanning) direction) Is forming.

  The misregistration inspection pattern formed at the left end in the main scanning direction is a pattern P_K_l_l for each of the colors K, C, M, and Y that is transferred and formed at regular intervals in the sub-scanning direction in parallel with the main scanning direction of the transfer belt 151. , P_C_l_l, P_M_l_l, and P_Y_l_l, and K, C, M, and Y colors that are formed obliquely at a constant angle with the main scanning direction of the transfer belt 151 and at regular intervals in the sub-scanning direction Patterns P_K_o_l, P_C_o_l, P_M_o_l, and P_Y_o_l are formed. Then, it should be corrected from the deviation between the calculated mutual distance of the patterns P_K_l_l, P_C_l_l, P_M_l_l, and P_Y_l_l predicted from the current writing timing setting and the actual mutual distance detected by the light detection sensor 120 Information about the color misregistration amount in the sub-scanning direction can be obtained. Further, the mutual distance in the sub-scanning direction of the patterns P_K_o_l, P_C_o_l, P_M_o_l, and P_Y_o_l predicted from the setting of the current writing timing and the mutual distance in the actual sub-scanning direction detected by the light detection sensor 120 Information about the amount of color misregistration in the main scanning direction to be corrected can be obtained from the misregistration. That is, since the patterns P_K_o_l, P_C_o_l, P_M_o_l, and P_Y_o_l are formed to be inclined with respect to the main scanning direction, the shift in the main scanning direction is converted into the sub scanning direction and detected.

  On the other hand, the misregistration inspection pattern formed at the right end in the main scanning direction is a pattern of each color of K, C, M, and Y that is transferred and formed at regular intervals in the sub scanning direction in parallel with the main scanning direction of the transfer belt 151. Each color of K, C, M, and Y, which is transferred and formed at a constant interval in the sub-scanning direction at an angle with P_K_l_r, P_C_l_r, P_M_l_r, P_Y_l_r, and the main scanning direction of the transfer belt 151. Patterns P_K_o_r, P_C_o_r, P_M_o_r, and P_Y_o_r are formed. The acquisition of information about the color misregistration amount is the same as that at the left end.

  The misregistration inspection pattern formed in the center of the main scanning direction is a pattern of each color of K, C, M, and Y that is transferred and formed at regular intervals in the sub-scanning direction in parallel with the main scanning direction of the transfer belt 151. Each color of K, C, M, and Y, which is transferred and formed obliquely at a constant interval in the sub-scanning direction at an angle with P_K_l_c, P_C_l_c, P_M_l_c, and P_Y_l_c and the main scanning direction of the transfer belt 151 Patterns P_K_o_c, P_C_o_c, P_M_o_c, and P_Y_o_c are formed. Acquisition of information about the color misregistration amount is the same as that at the left end or the right end.

  If the detection and correction of the color misregistration amount by forming such a color misregistration detection pattern on the transfer belt is performed every time a color image is formed, the color image forming operation is delayed for the user, and conversely the frequency If the amount is too small, there is a problem that color misregistration occurs in the color image finally formed on the recording paper.

  FIG. 7 shows the configuration of the optical scanning writing unit 101 of the image forming unit 9 of the color image forming apparatus 1.

  In the figure, laser diode (LD) units 201K, 201C, 201M, and 201Y are LD units corresponding to color components of K (black), C (cyan), M (magenta), and Y (yellow), respectively. Yes, and modulated and driven by the image formation control unit 110.

  The laser light K emitted from the LD unit 201K is collected by the collimator lens 202K, reaches the mirror 203K, and is reflected by the mirror 203K in the direction of the polygon motor 304. The laser beam K reflected by the polygon mirror 304 that is driven to rotate passes through an fθ lens 205KC (shared with C (cyan)), is reflected by the mirror 206K, and travels toward the photosensitive drum 102K. The laser light K is reflected by a mirror 207KC (shared with C (cyan)) disposed at a position off the mirror 206K and is incident on an optical sensor 208KC (shared with C (cyan)). A signal output when the laser beam K is detected by the sensor 208KC is used as a synchronization signal serving as a reference for the writing start timing in the main scanning direction in the image forming operation of the K color component. The laser beam K is scanned in the main scanning direction on the photosensitive drum 102K by the rotation of the polygon motor 204, and an electrostatic latent image corresponding to the image of the K color component is formed on the photosensitive drum 102K.

  The laser light C emitted from the LD unit 201C is collected by the collimator lens 202C and travels toward the polygon motor 304. The laser light C reflected by the polygon mirror 304 that is driven to rotate passes through an fθ lens 205KC (shared with K (black)), is reflected by the mirror 206C, and travels toward the photosensitive drum 102C. The laser light C is reflected by a mirror 207KC (shared with K (black)) disposed at a position off the mirror 206C and is incident on an optical sensor 208KC (shared with K (black)). A signal output by detecting the laser beam C by the sensor 208KC is used as a synchronization signal that serves as a reference for the writing start timing in the main scanning direction in the C color component image forming operation. The laser beam C is scanned in the main scanning direction on the photosensitive drum 102C by the rotation of the polygon motor 204, and an electrostatic latent image corresponding to an image of the C color component is formed on the photosensitive drum 102C.

  The laser beam Y emitted from the LD unit 201Y is collected by the collimator lens 202Y, reaches the mirror 203Y, and is reflected in the direction of the polygon motor 304 by the mirror 203Y. The laser beam Y reflected by the polygon mirror 304 that is driven to rotate passes through an fθ lens 205YM (shared with M (magenta)), is reflected by the mirror 206Y, and travels toward the photosensitive drum 102Y. The laser beam Y is reflected by a mirror 207YM (shared with M (magenta)) arranged at a position off the mirror 206Y and is incident on an optical sensor 208YM (shared with M (magenta)). A signal output when the laser beam Y is detected by the sensor 208YM is used as a synchronization signal serving as a reference for the writing start timing in the main scanning direction in the image forming operation of the Y color component. The laser beam Y is scanned on the photosensitive drum 102Y in the main scanning direction by the rotation of the polygon motor 204, and an electrostatic latent image corresponding to the image of the Y color component is formed on the photosensitive drum 102Y.

  The laser light M emitted from the LD unit 201M is collected by the collimator lens 202M and travels toward the polygon motor 304. The laser beam M reflected by the polygon mirror 304 that is driven to rotate passes through the fθ lens 205YM (shared with Y (yellow)), is reflected by the mirror 206M, and travels toward the photosensitive drum 102M. The laser light M is reflected by a mirror 207YM (shared with Y (yellow)) disposed at a position off the mirror 206M and is incident on an optical sensor 208YM (shared with Y (yellow)). A signal output by detecting the laser beam M by the sensor 208YM is used as a synchronization signal that serves as a reference for the writing start timing in the main scanning direction in the image forming operation of the M color component. The laser light M is scanned in the main scanning direction on the photosensitive drum 102M by the rotation of the polygon motor 204, and an electrostatic latent image corresponding to the image of the M color component is formed on the photosensitive drum 102M.

  However, in the optical scanning writing unit 101 configured as shown in FIG. 7, color misregistration due to the arrangement accuracy of each component corresponding to each color component of KCMY and the lens formation accuracy, that is, on the transfer belt 151. There was a relative shift in the formation position of the image of each color component constituting the color image formed in an overlapping manner.

  For such color misregistration caused by the arrangement and formation accuracy of each component corresponding to each color component, adjustment called skew adjustment that changes the reflection angle of the mirror and control of image writing start timing are performed. Thus, the adjustment in the main scanning direction is performed, and the image expansion and contraction in the main scanning direction is adjusted by controlling the writing clock frequency. That is, in the image formation of the color component relatively extended in the main scanning direction, the writing clock frequency is set to a high value, and in the image formation of the color component relatively compressed in the main scanning direction, the write clock is set. Adjustments were made by setting the frequency to a low level.

  However, in such an adjustment method, the position shift (the entire line level in the main scanning direction) such as the adjustment of the writing start position in the main scanning direction for each color component and the adjustment of the main scanning line length for each color component ( It is only possible to correct (color misregistration), and it is impossible to make adjustments for irregular fluctuations at the pixel level in the main scanning direction caused by local distortion of the lens due to temperature changes.

  FIG. 9 schematically shows a color shift at the pixel level in the main scanning direction when there is no correction of the write timing.

  As shown in FIG. 6A, when writing is performed for each of the black (Bk) and yellow (Yellow) color components with an uncorrected write clock (the clock cycle corresponding to each pixel is the same), transfer is performed. In the superimposed image formed on the belt, as shown in FIG. 4B, color misregistration at the pixel level occurs in the main scanning direction. In FIG. 4B, each vertical line indicates the recording position of each pixel, the solid line indicates a black (Bk) pixel, and the dotted line indicates a yellow (Yellow) pixel.

  Such pixel-level color misregistration cannot be completely corrected by forming and detecting a misregistration inspection pattern as shown in FIG. This is because the correction by the misregistration inspection pattern can deal only with the global color misregistration as the entire main scanning line.

  Therefore, in the best mode for carrying out the present invention, by changing the clock cycle corresponding to each pixel as shown in FIG. 10 (a), the pixel level as shown in FIG. 10 (b) is obtained. Corrects local color misregistration.

  Further, the local positional deviation amount at the pixel level in the main scanning direction varies with time (temperature fluctuation). FIG. 11 schematically shows this.

  The vertical solid line in FIG. 10A indicates the pixel formation position in the main scanning direction when the apparatus is activated for the specific color component, and the vertical dotted line in FIG. The pixel formation position in the main scanning direction when time has elapsed is shown. FIG. 4B shows the relationship of FIG. 2A when the horizontal axis is the pixel order, and the vertical axis is the variation amount of the formation position deviation from the normal position (equal interval) in each pixel. ing.

  As described above, even if the local positional deviation (mutual deviation of the pixel formation position) at the pixel level between the color components is corrected at the time of start-up, for example, the amount of color deviation for each color component is increased over time (temperature fluctuation). Because it fluctuates, it is necessary to take this into consideration.

  FIG. 12 shows an example of an image forming process procedure in the color image forming apparatus 1. This image forming process procedure corresponds to the image forming control means.

  In the figure, the CPU 2 measures the temperature of the optical scanning writing unit 130 by the temperature sensor 130 via the image formation control unit 110 of the image forming unit 9 (processing S101).

  Then, the measured temperature is collated with the table 5a of FIG. 3 to identify the corresponding main scanning direction positional deviation amount information (processing S102). Then, write clock generation timing information is generated based on the specified positional deviation amount information and stored in the RAM as shown in FIG. 4 (processing S103). The write clock generation timing information 4a is specifically information on the length of the clock cycle for each pixel in the main scanning direction, and the write clock generation timing information from the beginning is used as the positional deviation amount information in the main scanning direction. Although it is possible to save the time and effort of generation by setting, since the table 5a needs to store information on the amount of positional deviation in the main scanning direction for many temperatures, local positional deviation at the pixel level that is the basis of generation is required. By storing information about the amount in the table 5a and generating the write clock generation timing information as necessary, the storage capacity required for the table 5a can be reduced.

  Then, the storage address of the image data to be formed in the RAM 4 is given to the image formation control unit 110 of the image forming unit 9 and the start of the image formation operation is instructed to perform the image formation control process on the image formation control unit 110 (Processing S104). In the processing S104, the write clock generation timing information 4a is referred to, and the local color shift at the pixel level in the main scanning direction can be most optimally corrected at the current temperature of the optical scanning writing unit.

  In the image forming processing procedure shown in FIG. 12, when color image data of a plurality of pages is continuously formed, every time one page image is formed, every time one page is formed, one image is formed. As described above, the execution frequency may be increased. Thereby, even if the temperature of the image forming unit 9 changes due to successive image forming operations, it is possible to accurately correct the positional deviation in the image formation of each page. According to the present invention, the misalignment correction performed by measuring the temperature of the image forming unit 9 and correcting the writing clock based on the main scanning direction misalignment amount information collected in advance corresponding to the measured temperature is short. Since it can be executed in time, there is almost no delay in the image forming operation.

  12 is not performed every time a color image forming operation is performed, but when there is a certain temperature variation (for example, 3 ° C.) from the temperature when the previous processing S101 to S103 is performed. As long as the processes S101 to S103 are controlled to be performed this time, the process S101 to S103 may not be performed wastefully even though the amount of positional deviation is small because the temperature fluctuation is small.

  FIG. 13 shows another example of the image forming process procedure in the color image forming apparatus 1 different from that shown in FIG.

  In the figure, the CPU 2 measures the temperature of the optical scanning writing unit 130 with the temperature sensor 130 via the image formation control unit 110 of the image forming unit 9 (processing S201).

  Then, the measured temperature is collated with the table 5a of FIG. 3 to specify the corresponding main scanning direction positional deviation amount information (processing S202). Then, write clock generation timing information is generated based on the specified positional deviation amount information and stored in the RAM as shown in FIG. 4 (process S203).

  7 is formed on the transfer belt 151 (process S204), the formed misalignment inspection pattern is read by the light detection sensor 120 (process S205), and the read misalignment amount is obtained. Based on the above, after correcting the positional deviation in the sub-scanning direction and the global positional deviation of the entire line in the main scanning direction by correcting the write clock generation timing information (processing S206), the image forming unit 9 By passing the storage address of the image data to be formed in the RAM 4 to the image formation control unit 110 and instructing the start of the image formation operation, the image formation control unit 110 is caused to perform image formation control processing (processing S207). In the processing S207, the write clock generation timing information 4a is referred to, and not only can the local color shift at the pixel level in the main scanning direction be most optimally corrected at the current temperature of the optical scanning writing unit, but also the main scanning. It is also possible to correct a global positional shift of the entire main scanning line that cannot be handled by the direction positional shift amount information.

  FIG. 14 shows another example of an image forming process procedure in the color image forming apparatus 1.

  In the figure, the CPU 2 measures the temperature of the optical scanning writing unit 130 by the temperature sensor 130 via the image formation control unit 110 of the image forming unit 9 (processing S301).

  Then, the measured temperature is collated with the table 5a of FIG. 3 to specify the corresponding main scanning direction positional deviation amount information (processing S302). Then, write clock generation timing information is generated based on the specified positional deviation amount information, and stored in the RAM as shown in FIG. 4 (processing S303).

Then, through the operation display unit 7, whether or not a misregistration inspection instruction operation input has been made, that is, prior to the start of the current image forming operation, an instruction to perform a misregistration inspection for the current image forming operation is issued. Then, it is confirmed whether a predetermined key is pressed or the mode is set (step S304). If there is no instruction (No in S305), the process proceeds to S309. If there is an instruction (Yes in judgment S305), the misalignment inspection pattern shown in FIG. 7 is formed on the transfer belt 151 (process S306), and the formed misalignment inspection pattern is read by the light detection sensor 120. (Processing S307) Based on the read misregistration amount, correction of misalignment in the sub-scanning direction and global misalignment of the entire line in the main scanning direction are corrected by correcting the write clock generation timing information. Above (processing S308), the storage address of the image data to be formed in the RAM 4 is given to the image forming control unit 110 of the image forming unit 9 and the start of the image forming operation is instructed. The formation control process is performed (process S309). In the process S309, the writing clock generation timing information 4a is referred to, and not only can the local color shift at the pixel level in the main scanning direction be most optimally corrected at the current temperature of the optical scanning writing unit,
When there is an instruction from the user, it is possible to correct a global positional shift of the entire main scanning line that cannot be handled by the main scanning direction positional shift amount information. The operations for forming / reading the misalignment inspection pattern in Steps S306 and S307 are recognized as part of the image forming operation for the user, and the image forming operation takes time. By performing this only when there is a specific instruction, it is possible to balance the improvement of the image quality of the formed image by correcting the color misregistration and the reduction of the time required for image formation.

  FIG. 15 shows another example of an image forming process procedure in the color image forming apparatus 1.

  In the figure, the CPU 2 measures the temperature of the optical scanning writing unit 130 by the temperature sensor 130 via the image formation control unit 110 of the image forming unit 9 (processing S401).

  Then, the measured temperature is collated with the table 5a in FIG. 3 to specify the corresponding main scanning direction positional deviation amount information (processing S402). Then, write clock generation timing information is generated based on the specified positional deviation amount information and stored in the RAM as shown in FIG. 4 (processing S403).

  Then, the temperature difference between the temperature Tcurrent and the temperature Tprev measured in the process S401 is confirmed (process S404). The temperature Tprev is set in step S406, and indicates the temperature of the image forming unit 9 when an image forming operation is performed with color misregistration correction by the previous misregistration inspection pattern.

  If the temperature difference between the temperature Tcurrent and the temperature Tprev is not equal to or greater than a predetermined threshold temperature difference (for example, 5 ° C.) (No in S405), the process proceeds to S410. When the temperature difference is not less than the threshold temperature difference (for example, 5 ° C.) (Yes in determination S405), the current temperature Tcurrent measured in the process S401 is set as the temperature Tprev (process S406), and the position shown in FIG. A misalignment inspection pattern is formed on the transfer belt 151 (process S407), and the formed misalignment inspection pattern is read by the light detection sensor 120 (process S408). Based on the read misalignment amount, the sub-scanning direction is measured. Along with the correction of the positional deviation, the overall positional deviation of the entire line in the main scanning direction is corrected by correcting the write clock generation timing information (processing S409), and then the image forming control unit 110 of the image forming unit 9 is corrected. By passing the storage address of the image data to be formed in the RAM 4 and instructing the start of the image forming operation to the image forming control unit 110. To perform the image formation control processing (processing S410). In the processing S410, the write clock generation timing information 4a is referred to, and the local color shift at the pixel level in the main scanning direction can be corrected most optimally at the current temperature of the optical scanning writing unit. When the temperature difference from when the misalignment correction is performed by the misalignment inspection pattern continues to exceed the temperature difference, that is, when the overall misalignment amount of the entire main scan line is considered to increase due to the temperature change Therefore, it is possible to correct a global positional shift of the entire main scanning line which cannot be handled by the positional deviation amount information in the main scanning direction. The operations for forming and reading the misalignment inspection pattern in steps S406 and S307 are recognized as a part of the image forming operation by the user, and the image forming operation takes time. This is not done every time, but only when there is a certain temperature change, automatically balancing the improvement of the image quality of the formed image by correcting the color shift and the reduction of the time required for image formation. Can take.

  FIG. 16 shows another example of an image forming process procedure in the color image forming apparatus 1.

  The processing procedure shown in the figure is a modification of the processing procedure shown in FIG. 13, and the CPU 2 controls the temperature of the optical scanning writing unit 130 by the temperature sensor 130 via the image formation control unit 110 of the image forming unit 9. Measure (Process S501).

  Then, the measured temperature is collated with the table 5a of FIG. 3 to specify the corresponding main scanning direction positional deviation amount information (processing S502). Then, write clock generation timing information is generated based on the specified positional deviation amount information and stored in the RAM as shown in FIG. 4 (process S503).

  7 is formed on the transfer belt 151 (process S504), the formed misalignment inspection pattern is read by the light detection sensor 120 (process S505), and the read misregistration amount is formed. The correction of the positional deviation in the sub-scanning direction and the overall positional deviation of the entire line in the main scanning direction are corrected by correcting the write clock generation timing information (processing S506), and the read positional deviation. Based on the amount, the main scanning direction positional deviation amount information corresponding to the temperature measured in step S501 in the table 5a of FIG. 3 is updated (step S507). Then, the storage address of the image data to be formed in the RAM 4 is given to the image formation control unit 110 of the image forming unit 9 and the start of the image formation operation is instructed to perform the image formation control process on the image formation control unit 110 (Processing S508). In the processing S508, the write clock generation timing information 4a is referred to, and not only can the local color shift at the pixel level in the main scanning direction be most optimally corrected at the current temperature of the optical scanning writing unit, but also the main scanning. It is also possible to correct a global positional shift of the entire main scanning line that cannot be handled by the direction positional shift amount information. Further, the positional deviation amount information set in the table 5a of FIG. 3 is not fixed, but is corrected based on positional deviation amount information obtained by reading the positional deviation inspection pattern. It is possible to correct the positional deviation in the main scanning direction with high accuracy by reflecting this change in the positional deviation amount information set in the table 5a of FIG.

  Although the best mode for carrying out the present invention has been described above, it is needless to say that the present invention is not limited to the above and can be variously modified without departing from the gist thereof. .

1 is a diagram showing a system configuration including a color image forming apparatus according to the best mode for carrying out the present invention. 1 is a block diagram of a color image forming apparatus according to the best mode for carrying out the present invention. It is a figure which shows about the memory content of EEPROM of the color image forming apparatus which concerns on the best form for implementing this invention. It is a figure which shows about the memory content of RAM of the color image forming apparatus which concerns on the best form for implementing this invention. 1 is a diagram illustrating a configuration of an image forming unit of a color image forming apparatus according to the best mode for carrying out the present invention. FIG. 6 is a diagram showing a configuration different from that of FIG. 5 of the image forming unit of the color image forming apparatus according to the best mode for carrying out the present invention. FIG. 4 is a diagram showing a color misregistration detection pattern formed on a transfer belt. 1 is a diagram showing a configuration of an optical scanning writing unit of a color image forming apparatus according to the best mode for carrying out the present invention. FIG. 6 is a schematic diagram for explaining color misregistration in the main scanning direction when there is no correction of writing timing. FIG. 10 is a schematic diagram for explaining that the color shift in the main scanning direction is eliminated by correcting the writing timing. It is a figure which shows typically about the time-dependent change of the color shift of the main scanning direction about a specific color. 5 is a flowchart illustrating an example of an image forming process procedure in the color image forming apparatus according to the best mode for carrying out the present invention. 5 is a flowchart illustrating an example of an image forming process procedure in the color image forming apparatus according to the best mode for carrying out the present invention. 5 is a flowchart illustrating an example of an image forming process procedure in the color image forming apparatus according to the best mode for carrying out the present invention. 5 is a flowchart illustrating an example of an image forming process procedure in the color image forming apparatus according to the best mode for carrying out the present invention. 5 is a flowchart illustrating an example of an image forming process procedure in the color image forming apparatus according to the best mode for carrying out the present invention.

Explanation of symbols

1 Color image forming apparatus 2 CPU
3 RAM
4 ROM
5 EEPROM
6 Clock circuit 7 Operation display unit 8 Image reading unit 9 Image forming unit 10 Image processing unit 11 LAN communication control unit 12 Communication control unit 13 NCU unit 14 System bus

Claims (12)

The intensity of the laser light in synchronism with the write clock generated based on the write clock generation timing information that defines the write timing of each pixel in the main scanning direction for the image data of each color component constituting the color image data to be formed And forming an electrostatic latent image by irradiating the photosensitive member corresponding to each color component to a toner image by a developing device corresponding to each color component, and applying the toner image on a transfer medium. In a color image forming apparatus provided with image forming means for superimposing on
The amount of positional deviation in the main scanning direction, which is information about the amount of positional deviation of the pixel level in the main scanning direction of the image of each color component formed on the transfer medium, collected in advance by changing the temperature of the image forming means. Temperature / main-scanning direction displacement information storage means for storing information;
Temperature measuring means for measuring the temperature of the image forming means;
Prior to the start of the color image forming operation by the image forming unit, the current temperature of the image forming unit measured by the temperature measuring unit is compared with the temperature / main scanning direction positional deviation amount information storage unit and corresponding main scanning is performed. Image forming control means for specifying direction positional deviation amount information and setting the write clock generation timing information based on the specified main scanning direction positional deviation amount information;
A color image forming apparatus capable of correcting a position shift optimum for a current temperature in a color image forming operation in the image forming means.   The image formation control unit includes a current temperature of the image forming unit measured by the temperature measurement unit prior to the start of a color image forming operation by the image forming unit, and a temperature / main scanning direction positional deviation amount information storage unit. The corresponding main scanning direction positional deviation amount information is identified by collation, and the write clock generation timing information is set based on the identified main scanning direction positional deviation amount information, and then the image forming unit sets the information on the transfer medium. A misregistration inspection pattern is formed at the same time and is read by a predetermined reading means to obtain a global misregistration amount of the entire line in the main scanning direction, and the write clock generation timing information is obtained based on the obtained misregistration amount. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is to be corrected.   The image formation control unit includes a current temperature of the image forming unit measured by the temperature measurement unit prior to the start of a color image forming operation by the image forming unit, and a temperature / main scanning direction positional deviation amount information storage unit. The corresponding main scanning direction positional deviation amount information is identified by collation, the writing clock generation timing information is set based on the identified main scanning direction positional deviation amount information, and then the transfer medium is used by the image forming unit. A misalignment inspection pattern is formed on the read line and read by a predetermined reading means to obtain a global misalignment amount of the entire line in the main scanning direction, and the write clock generation timing information based on the obtained misalignment amount In addition, the correction by the formation / reading of the misregistration inspection pattern is performed only when there is a predetermined instruction operation input. The color image forming apparatus according to claim 1, characterized in that.   The image formation control unit includes a current temperature of the image forming unit measured by the temperature measurement unit prior to the start of a color image forming operation by the image forming unit, and a temperature / main scanning direction positional deviation amount information storage unit. The corresponding main scanning direction positional deviation amount information is identified by collation, the writing clock generation timing information is set based on the identified main scanning direction positional deviation amount information, and then the transfer medium is used by the image forming unit. A misalignment inspection pattern is formed on the read line and read by a predetermined reading means to obtain a global misalignment amount of the entire line in the main scanning direction, and the write clock generation timing information based on the obtained misalignment amount The correction by forming and reading the misalignment inspection pattern is measured by the temperature measuring means at the previous correction. 2. The color according to claim 1, which is performed only when the difference between the measured temperature and the temperature measured by the temperature measuring means during the current color image forming operation is equal to or greater than a predetermined temperature difference. Image forming apparatus.   The image formation control unit includes a current temperature of the image forming unit measured by the temperature measurement unit prior to the start of a color image forming operation by the image forming unit, and a temperature / main scanning direction positional deviation amount information storage unit. The corresponding main scanning direction positional deviation amount information is identified by collation, and the write clock generation timing information is set based on the identified main scanning direction positional deviation amount information, and then the image forming unit sets the information on the transfer medium. A misalignment inspection pattern is formed at the same time and is read by a predetermined reading means to obtain a global misalignment amount of the entire line in the main scanning direction, and the write clock generation timing information is obtained based on the obtained misalignment amount. At the same time, the temperature / main scanning direction positional deviation amount information is added to the current temperature of the image forming unit based on the obtained positional deviation amount. The color image forming apparatus according to claim 1, characterized in that the corresponding is intended to correct the main scanning direction positional shift amount information in the storage unit.   The main scanning direction positional deviation amount information collected for each temperature of the image forming means stored in the temperature / main scanning direction positional deviation amount information storage means is a predetermined positional deviation detection pattern by the image forming means. 6. The color image formation according to claim 1, wherein the color image is formed by being formed on the transfer medium, transferred to a recording paper, and collected by reading the output recording paper. apparatus.   The main-scanning-direction positional deviation amount information collected for each temperature of the image forming unit, which is stored in the temperature / main-scanning-direction positional deviation amount information storage unit, corresponds to a main scanning corresponding to a predetermined positional deviation detection pattern. 6. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is collected by directly reading laser light deflected in a direction.   The image formation control unit includes a current temperature of the image forming unit measured by the temperature measurement unit prior to the start of a color image forming operation by the image forming unit, and a temperature / main scanning direction positional deviation amount information storage unit. The corresponding main scanning direction positional deviation amount information is identified by collation, and the write clock generation timing information is set based on the identified main scanning direction positional deviation amount information. 2. The method according to claim 1, wherein the measurement is performed only when the difference between the temperature measured by the measuring unit and the temperature measured by the temperature measuring unit during the current color image forming operation is equal to or greater than a predetermined temperature difference. The color image forming apparatus described in 1.   In the case where color image formation is continuously performed, the image formation control unit is configured to measure the temperature measured by the temperature measurement unit for each page or each document prior to the start of the color image formation operation by the image formation unit. The current temperature of the image forming means is collated with the temperature / main scanning direction positional deviation amount information storage means to identify corresponding main scanning direction positional deviation amount information, and based on the identified main scanning direction positional deviation amount information. The color image forming apparatus according to claim 1, wherein the write clock generation timing information is set.   2. A color image forming apparatus according to claim 1, wherein the deflecting means for irradiating the laser beam onto the photosensitive member corresponding to each color component is a polygon motor.   2. The color image forming apparatus according to claim 1, wherein the temperature measuring unit measures a temperature or a temperature distribution of an fθ lens constituting the image forming unit.   The color image forming apparatus according to claim 1, wherein the temperature measuring unit is a thermocouple.