JP2015077730A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device enabling correction of image distortion in which displacement amount in axial direction of a photoreceptor is different in rotation direction of the photoreceptor.SOLUTION: An image formation device includes a photoreceptor drum which is rotatably provided around a rotational axis, an exposure device in which a plurality of light emitting elements are arrayed in the direction of rotational axis, for exposure by illuminating the plurality of light emitting elements to the photoreceptor drum, and a plurality of dual ports RAM130 for storing image data for making a light emitting element illuminate for each of at least two light emitting element groups arrayed in the rotation axis direction, among the plurality of light emitting elements. By changing a reading cycle for reading image data from the plurality of dual ports RAM130, a light emission interval on the photoreceptor drum is changed for each light emitting element group.

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, in an image forming apparatus, when a recording sheet is conveyed to an image forming unit, for example, image distortion occurs due to various factors such as image distortion due to recording sheet conveyance failure. As a technique capable of correcting image distortion generated in such an image forming apparatus, for example, those described in Patent Document 1, Patent Document 2, and the like have already been proposed.

  Patent Document 1 is supplied by a registration roller or a fixing device in order to provide an LED printer that can correct the print length of the front end area and the rear end area of a paper in an LED printer using a split LED head. A print control circuit that detects the position of the print medium being printed and adjusts the print timing of the first partial LED head and the second partial LED head according to the detected position and the LED head interval. It is composed.

  Patent Document 2 discloses an image forming apparatus that can obtain an appropriate image output even if the LED array unit is misaligned in the sub-scanning direction. In order to obtain image data without image data, fine adjustment change magnification setting means for accepting setting of fine adjustment change magnification when image data is finely changed, and image data according to the fine adjustment change magnification set by the fine adjustment change magnification setting means And a fine scaling unit for changing the generation period interval of the line synchronization signal based on the calculation of the calculation unit.

JP 2008-233858 A JP-A-2005-170033

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of correcting image distortion in which the amount of positional deviation in the axial direction of the photoconductor differs in the rotation direction of the photoconductor.

According to a first aspect of the present invention, there is provided a photoreceptor provided to be rotatable around a rotation axis;
A plurality of light emitting elements arranged along the direction of the rotation axis, and exposure means for performing exposure by causing the plurality of light emitting elements to emit light to the photoconductor;
A plurality of storage means for storing image data for causing the light emitting elements to emit light for each of at least two light emitting element groups arranged in the direction of the rotation axis among the plurality of light emitting elements;
With
The image forming apparatus is characterized in that a light emission interval on the photoconductor is changed for each light emitting element group by changing a reading cycle for reading the image data from the plurality of storage units.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the plurality of storage units include a dual port RAM having ports on the image information writing side and the reading side, respectively. Device.

  According to a third aspect of the present invention, the plurality of dual port RAMs are arranged along the direction of the rotation axis, and writing to each dual port RAM is performed continuously for one line, and each dual port RAM is The image forming apparatus according to claim 2, wherein reading from the RAM is performed for each light emitting element group of the exposure unit.

  The invention described in claim 4 includes correction information generation means for generating correction information of an image along the rotation direction of the photosensitive member in the axial direction, and the plurality of dual port RAMs include the correction information generation means. 4. The image forming apparatus according to claim 2, wherein both the writing time and the reading time of the image information are changed based on the correction information generated by the above.

  According to a fifth aspect of the present invention, the change in the light emission interval on the photoconductor is based on the correction information generated by the correction information generating unit, and the image information is changed in units of pixels along the axial direction. The image forming apparatus according to claim 4, wherein the image forming apparatus is changed.

  The invention described in claim 6 is characterized in that the correction information generation unit generates correction information based on image information obtained by reading a predetermined image distortion detection image output from the image forming apparatus. An image forming apparatus according to claim 4 or 5.

  The invention described in claim 7 is characterized in that the correction information generating means generates correction information by the user selecting from a plurality of predetermined correction information. The image forming apparatus described.

  According to the first aspect of the present invention, it is possible to correct image distortion in which the amount of positional deviation in the axial direction of the photoconductor differs in the rotation direction of the photoconductor as compared with the case where the configuration is not provided.

  According to the second aspect of the present invention, it is possible to perform image correction by changing the timing of writing or reading image information, compared with the case where the configuration is not provided.

  According to the third aspect of the present invention, the time required for image writing can be shortened as compared with the case where the configuration is not provided.

  According to the fourth aspect of the present invention, the degree of freedom of the correction amount for correcting the positional deviation in the axial direction of the photoconductor in the rotation direction of the photoconductor can be increased as compared with the case where the configuration is not provided. .

  According to the fifth aspect of the present invention, it is possible to easily correct the positional deviation of the image along the axial direction of the photosensitive member as compared with the case where the configuration is not provided.

  According to the sixth aspect of the present invention, it is possible to correct image distortion based on the image actually output from the image forming apparatus, as compared with the case where the configuration is not provided.

  According to the invention described in claim 7, it is possible to easily generate the correction information of the image as compared with the case where the configuration is not provided.

1 is a schematic configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. It is a block diagram which shows exposure apparatus. It is a plane block diagram which shows exposure apparatus. It is a block diagram which shows the LED element of exposure apparatus. It is a graph which shows explanatory drawing which shows the mechanism of the image distortion which arises on a recording paper. It is a schematic diagram which shows the image distortion which arises on a recording paper. 1 is a block diagram showing a control circuit of an image forming apparatus according to Embodiment 1 of the present invention. It is explanatory drawing which shows the arrangement | sequence of a memory. It is a circuit diagram which shows dual port RAM. It is a timing chart which shows a line sync signal. It is explanatory drawing which shows the image distortion which arises in a test chart. It is explanatory drawing which shows the correction | amendment operation | movement of an image distortion. It is a graph which shows the correction | amendment state of the write-in and read-out period of dual port RAM. It is a timing chart which shows the corrected line sync signal. It is explanatory drawing which shows the correction state of the image along the main scanning direction. It is explanatory drawing which shows the effect by the correction | amendment of the write-in and read-out period of dual port RAM. It is a schematic diagram which shows the operation part of the image forming apparatus which concerns on Embodiment 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIG. 1 shows an overview of the entire image forming apparatus according to the first embodiment.

<Overall Configuration of Image Forming Apparatus>
The image forming apparatus 1 according to the first embodiment is configured as a color copying machine, for example. The image forming apparatus 1 includes an image reading device 3 that reads an image of a document 6 and an image forming unit 2 as an example of an image forming unit that forms an image on a recording medium based on image data. The image reading device 3 is disposed in a state of being supported by the support unit 4 above the device main body 1a that houses the image forming unit 2, and an image is formed between the image reading device 3 and the device main body 1a. A space for discharging the recorded recording medium is formed.

The image reading device 3 is provided with a control panel 110 as an operation unit for operating the image forming device I and the image reading device 2. The control panel 110 has a touch panel 111 that also serves as a display unit that displays an operation menu, warnings, messages, and the like to the user and receives various settings for the displayed operation menu, and a plurality of operation buttons 112.

  The image forming unit 2 holds a plurality of image forming apparatuses 10 that form toner images developed with toner constituting the developer, and the toner images formed by the respective image forming apparatuses 10, and finally records media As an example, an intermediate transfer device 20 that transports the recording paper 5 to a secondary transfer position for secondary transfer, and a feeding that accommodates and transports the required recording paper 5 to be supplied to the secondary transfer position of the intermediate transfer device 20. A paper device 50 and a fixing device 40 for fixing the toner image on the recording paper 5 secondarily transferred by the intermediate transfer device 20 are provided. The apparatus main body 1a is formed of a support structure member, an exterior cover, and the like.

  The image forming device 10 includes four image forming devices 10Y, 10M, 10C, and 10K that respectively form four color toner images exclusively for yellow (Y), magenta (M), cyan (C), and black (K). It is configured. The four image forming apparatuses 10 (Y, M, C, K) are arranged in a line in the internal space of the apparatus main body 1a.

  As shown in FIG. 1, each image forming device 10 (Y, M, C, K) includes a photosensitive drum 11 as an example of a rotating image holding member, and around the photosensitive drum 11. The following devices are mainly arranged. The main devices are a charging device 12 that charges a peripheral surface (image holding surface) on the photosensitive drum 11 on which an image can be formed to a required potential, and image information (on the charged peripheral surface of the photosensitive drum 11). Exposure device 13 as exposure means for irradiating light based on (signal) to form an electrostatic latent image (for each color) having a potential difference, and corresponding colors (Y, M, C, K) for the electrostatic latent image ) Developing device 14 (Y, M, C, K) as developing means to develop a toner image by developing the toner, and a primary transfer device 15 for transferring each toner image to the intermediate transfer device 20; A drum cleaning device 16 (not shown) that removes and removes adherents such as toner remaining on the image holding surface of the photosensitive drum 11 after the primary transfer.

  The photosensitive drum 11 is formed by forming an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material on the peripheral surface of a cylindrical or columnar base material to be grounded. The photosensitive drum 11 is supported so as to rotate in a direction indicated by an arrow A that is a first direction (a rotating direction of the photosensitive member) when power is transmitted from a rotation driving device (not shown).

  The charging device 12 includes a contact-type charging roll that is disposed in contact with the photosensitive drum 11. A charging voltage is supplied to the charging device 12. As the charging voltage, when the developing device 14 performs reversal development, a voltage or current having the same polarity as the charging polarity of the toner supplied from the developing device 14 is supplied.

  The exposure device 13 forms an electrostatic latent image by irradiating the circumferential surface of the charged photosensitive drum 11 with light configured according to image information input to the image forming apparatus 1. Is. As will be described in detail later, the exposure apparatus 13 includes an LED array 33 in which LED elements are linearly arranged at a predetermined pitch along the axial direction of the photosensitive drum 11, and each LED element of the LED array 33. A rod lens array 34 that images the emitted light in a spot shape on the photosensitive drum 11 is provided. When the latent image is formed, the exposure device 13 receives information (signal) of an image input to the image forming device 1 by an arbitrary means and subjected to image processing by the image processing unit.

As shown in FIG. 2, the solid scanning exposure apparatus 13 is composed of an LED print head (LPH). The solid scanning exposure apparatus 13 includes a casing 31 that is elongated along the axial direction (second direction) of the photosensitive drum 11, and an LED array is provided on the surface of the casing 31. An LED circuit board 32 having 33 is mounted. Further, as shown in FIG. 3, a plurality of LED array chips 33 _{1 to} 33 _n constituting the LED eyelet 33 are staggered on the surface of the LED circuit board 32 so as to partially overlap in the longitudinal direction. Are arranged in a shape. The light beam emitted from the LED array 33 is narrowed by the rod lens array 34 as shown in FIG. The rod lens array 34 is attached to a holding member 35, and is attached to the housing 31 of the solid scanning exposure apparatus 13 by a plate spring S via the holding member 35.

  Further, as shown in FIG. 3, the LED circuit board 32 has a drive circuit 36 for causing the LED array 33 to emit light according to image information, a storage element 37 for storing image data, and a voltage applied to the LED array 33. Is provided at one end of the LED array 33. Furthermore, the LED circuit board 32 is connected to a wire harness 39 to which image data and control signals are sent from the control unit 5 described later. The drive circuit 36 of the LED circuit board 32 will be described in detail later. As the LED array 33, for example, a self-scanning LED array is used, but other types may be used.

  As shown in FIG. 4, the LED array 33 has LED elements arranged at a resolution of 1200 dpi (dot per inch) along the main scanning direction which is the axial direction (second direction) of the photosensitive drum 11. . The LED array 33 has a resolution of 2400 dpi along the sub-scanning direction that is the rotation direction (first direction) of the photosensitive drum 11.

  Each of the developing devices 14 (Y, M, C, K) holds the developer inside the casing in which the opening and the developer storage chamber are formed, and conveys it to the developing area facing the photosensitive drum 11. A developing roll, a stirring and conveying member such as two screw augers that convey the developer to be supplied to the developing roll while stirring, and a layer thickness regulation that regulates the amount (layer thickness) of the developer held by the developing roll It is configured by arranging members and the like. A developing bias voltage is supplied to the developing device 14 between the developing roll and the photosensitive drum 11 from a power supply device described later. Further, the developing roll and the agitating / conveying member rotate in a required direction by receiving power from a rotation driving device (not shown). As the four color developers (Y, M, C, K), for example, a two-component developer containing a non-magnetic toner and a magnetic carrier is used.

  The primary transfer device 15 is a contact-type transfer device including a primary transfer roll that rotates in contact with the peripheral surface of the photosensitive drum 11 and is supplied with a primary transfer voltage. As the primary transfer voltage, a DC voltage having a polarity opposite to the charging polarity of the toner is supplied from a power supply device (not shown).

  The drum cleaning device 16 is disposed so as to come into contact with the container-shaped main body, which is partially opened, and the peripheral surface of the photosensitive drum 11 after the primary transfer at a required pressure, and removes adhered matters such as residual toner to be cleaned. It consists of a cleaning plate and a collection device for collecting the deposits removed by the cleaning plate.

  As shown in FIG. 1, the intermediate transfer device 20 is disposed so as to exist at a position above each image forming device 10 (Y, M, C, K). The intermediate transfer device 20 includes an intermediate transfer belt 21 that rotates in a direction indicated by an arrow B while passing a primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roll), and an intermediate transfer belt 21. Are arranged on the outer peripheral surface (image holding surface) side of the intermediate transfer belt 21 supported by the belt support rolls 23 and a plurality of belt support rolls 22 to 24 that hold the belt in a desired state from the inner surface thereof and are rotatably supported. A secondary transfer device 25 for secondary transfer of the toner image on the intermediate transfer belt 21 to the recording paper 5, and a toner that remains and adheres to the outer peripheral surface of the intermediate transfer belt 21 after passing through the secondary transfer device 25; The belt cleaning device 26 mainly removes deposits such as paper dust and cleans it.

  As the intermediate transfer belt 21, for example, an endless belt made of a material in which a resistance adjusting agent such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin is used. The belt support roll 22 is configured as a driven roll, the belt support roll 23 is configured as a drive roll and a secondary transfer backup roll, and the belt support roll 24 is configured as a tension applying roll.

  As shown in FIG. 1, the secondary transfer device 25 is configured to move the intermediate transfer belt 21 at the secondary transfer position, which is the outer peripheral surface portion of the intermediate transfer belt 21 supported by the belt support roll 23 in the intermediate transfer device 20. This is a contact-type transfer device comprising a secondary transfer roll that rotates in contact with the peripheral surface and is supplied with a secondary transfer voltage. Further, a DC voltage having a polarity opposite or the same as the charging polarity of the toner is supplied as a secondary transfer voltage to the secondary transfer roll 25 or the support roll 23 of the intermediate transfer device 20.

  The fixing device 40 is in contact with a rotating rotator 41 in the form of a roll or belt heated by heating means so that the surface temperature is maintained at a predetermined temperature, and the rotating rotator 41 for heating at a required pressure. And a pressurizing rotator 42 in the form of a roll or a belt that rotates. In the fixing device 40, a contact portion where the heating rotator 41 and the pressing rotator 42 come into contact becomes a fixing processing unit that performs a required fixing process (heating and pressing).

The paper feeding device 50 is disposed so as to exist at a position below the image forming device 10 (Y, M, C, K). The paper feeding device 50 includes a plurality (or a single) of paper storage bodies 51 ₁ , 51 ₂ , 51 ₃ for storing recording paper 5 of a desired size, type, etc., and paper storage bodies 51 ₁ , 51. ₂ and 51 ₃ , and is mainly composed of sending devices 52 and 53 that feed the recording paper 5 one by one. The paper container 51 is attached so that it can be pulled out, for example, to the front side (side surface on which the user faces during operation) of the apparatus main body 1a.

  Between the paper feeding device 50 and the secondary transfer device 25, a plurality of paper conveyance roll pairs 54 and 55 for conveying the recording paper 5 delivered from the paper feeding device 50 to the secondary transfer position and a conveyance guide material are configured. A paper feeding / conveying path 56 is provided. A pair of sheet conveyance rolls 55 disposed at a position immediately before the secondary transfer position in the sheet conveyance path 56 is configured as a roll (registration roll) that adjusts the conveyance timing of the recording sheet 5, for example. Further, on the downstream side of the fixing device 40 in the paper conveyance direction, a discharge roll pair 58 that discharges the recording paper 5 to the discharge container 57 is disposed.

  The image forming apparatus 1 includes a double-sided conveyance path 59 that conveys the recording sheet 5 on which an image is formed on one side to the pair of sheet conveyance rolls 55 again with the front and back sides reversed. The double-sided conveyance path 59 includes a plurality of sheet conveyance roll pairs 60 and 61 and a conveyance guide material.

<Basic operation of image forming apparatus>
Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.

  Image formation when a full-color image formed by combining four color (Y, M, C, K) toner images using the four image forming devices 10 (Y, M, C, K) The operation will be described.

  When the image forming apparatus 1 receives command information for requesting an image forming operation (printing), the four image forming apparatuses 10 (Y, M, C, K), the intermediate transfer apparatus 20, the secondary transfer apparatus 30, and the fixing apparatus. 40 etc. starts.

  In each image forming device 10 (Y, M, C, K), each photoconductor drum 11 is first rotated in the direction indicated by an arrow A, and each charging device 12 makes a required surface of each photoconductor drum 11 on the surface. Each is charged to a polarity (negative polarity in the first embodiment) and a potential. Subsequently, the exposure apparatus 13 converts the image information input to the image forming apparatus 1 into each color component (Y, M, C, K) with respect to the surface of the photosensitive drum 11 after charging. Based on this signal, light is irradiated to form an electrostatic latent image of each color component constituted by a required potential difference on the surface.

  Subsequently, each developing device 14 (Y, M, C, K) has a corresponding color charged with a required polarity (minus polarity) with respect to the electrostatic latent image of each color component formed on the photosensitive drum 11. (Y, M, C, K) toners are respectively supplied and electrostatically adhered to perform development. By this development, the electrostatic latent images of the respective color components formed on the respective photosensitive drums 11 are visualized as toner images of four colors (Y, M, C, K) respectively developed with the corresponding color toners. It becomes.

  Subsequently, when each color toner image formed on the photosensitive drum 11 of each image forming device 10 (Y, M, C, K) is conveyed to the primary transfer position, the primary transfer device 15 causes each color image. The toner image is primarily transferred in such a manner that the toner image is sequentially superimposed on the intermediate transfer belt 21 rotating in the direction indicated by the arrow B of the intermediate transfer device 20.

  Further, in each image forming apparatus 10 for which the primary transfer has been completed, the drum cleaning device 16 cleans the surface of the photosensitive drum 11 by removing the adhering matter such as toner remaining on the surface of the photosensitive drum 11 so as to scrape off. . Thereby, each image forming apparatus 10 is brought into a state in which the next image forming operation can be performed.

  Subsequently, in the intermediate transfer device 20, the toner image primarily transferred by the rotation of the intermediate transfer belt 21 is held and conveyed to the secondary transfer position. On the other hand, the paper feeding device 50 sends out the required recording paper 5 to the paper feeding conveyance path 56 in accordance with the image forming operation. In the paper feed transport path 56, a pair of paper transport rolls 55 as registration rolls feeds the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

  At the secondary transfer position, the secondary transfer device 25 performs secondary transfer of the toner images on the intermediate transfer belt 21 onto the recording paper 5 collectively. Further, in the intermediate transfer device 20 after the secondary transfer is completed, the belt cleaning device 26 removes the adhering matter such as toner remaining on the surface of the intermediate transfer belt 21 after the secondary transfer, and cleans it.

  Subsequently, the recording sheet 5 on which the toner image is secondarily transferred is peeled off from the intermediate transfer belt 21 and the secondary transfer roll 25 and then conveyed to the fixing device 40. In the fixing device 40, a necessary fixing process (heating and pressing) is performed to fix the unfixed toner image on the paper 5. Finally, the recording paper 5 after the fixing is finished is discharged by a discharge roll pair 58 into a discharge storage portion 57 disposed at the upper part of the apparatus main body 1a.

  When images are formed on both sides of the recording paper 5, the paper 5 having an image formed on one side is conveyed to the discharge accommodating portion 57 by the second discharge roll pair 58, and the discharge roll pair 58 is formed on the paper 5. While holding the rear end, the rotation direction of the discharge roll pair 58 is switched from the discharge direction to the reverse direction, and the sheet 5 on which the image is formed on one side is reversed by a switching member (not shown) with the front and back sides reversed. It is sent out to the double-sided conveyance path 59. In the double-sided conveyance path 59, the recording paper 5 is conveyed to the paper conveyance roll pair 55 by the conveyance roll pairs 60 and 61, and the paper conveyance roll pair 55 sends the recording paper 5 to the secondary transfer position in accordance with the transfer timing. To do.

  As in the case of single-sided image formation, the recording paper 5 on which the toner image is secondarily transferred from the intermediate transfer belt 21 to the back surface at the secondary transfer position is subjected to a fixing process by the fixing device 40 and is then switched (not shown). The sheet is discharged by a pair of discharge rolls 58 through a member into a discharge container 57 arranged at the upper part of the housing 1a.

  Through the above operation, the recording paper 5 on which a full color image formed by combining four color toner images is output. When a monochrome image is formed, the image is formed only by the black image forming device 10K.

  By the way, in the image forming apparatus 1, in the secondary transfer portion that secondarily transfers the toner image from the intermediate transfer belt 21 to the recording paper 5, the recording paper 5 enters the secondary transfer portion as shown in FIG. 5. As a result, the stable position of the intermediate transfer belt 21 may change and the intermediate transfer belt 21 may meander. Further, depending on the transport state of the recording paper 5 to the secondary transfer unit, the recording paper 5 cannot be transported in a certain direction, and, for example, the transport direction of the rear end portion of the recording paper 5 is continuous. In some cases, the recording paper 5 may undergo secondary transfer while rotating, and as shown in FIG. 6, the rear end of the image may be distorted into a substantially “shi” shape.

<Configuration of Characteristic Part of Image Forming Apparatus>
FIG. 7 is a block diagram illustrating a control circuit of the image forming apparatus.

  Reference numeral 100 denotes a control unit including electronic components such as a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory) that control the operation of the image forming apparatus 1. Overall control. The image processing unit 101 performs predetermined image processing such as shading correction, lightness / color space conversion, gamma correction, and frame removal on image data read by the image reading device 3 and image data input from the outside. It is something to apply. The image distortion detection unit 102 is based on a test chart as an image distortion detection image read by the image reading device 3 and image data of a test chart read by an image reading device or a scanner of another device. Image distortion along the sub-scanning direction is detected. The correction value calculation unit 103 corrects the image distortion using a predetermined correction value arithmetic expression based on the image distortion along the main scanning direction and the sub-scanning direction detected by the image distortion detection unit 102. Is calculated. The correction unit 104 performs a correction process on the image along the main scanning direction based on the correction value calculated by the correction value calculation unit 103 and generates a correction signal for correcting the image along the sub-scanning direction. To do.

Reference numeral 36 denotes a drive circuit provided on the LED circuit board 32 of the exposure apparatus 13. The drive circuit 36 includes an image data development unit 105, a line sync signal correction unit 106, a timing signal generation unit 107, a reference clock generation unit 108, and output units 109 _{1 to} 109 ₁₂₈ . Image data is input as a serial signal from the correction unit 104 to the image data development unit 105. The image data development unit 105 includes, for example, a dual port RAM as a storage unit provided with two ports for writing image data and reading image data.

The line sync signal correction unit 106 is connected to the control unit 100, the correction unit 104, and the reference clock generation unit 108. Based on the reference clock signal from the reference clock generation unit 108, the line sync signal correction unit 106 generates a reference horizontal synchronization (line sync) signal ( Lsync ) from the control unit 100 based on the correction signal from the correction unit 104. To generate a corrected line sync signal. More specifically, the line sync signal correction unit 106 determines the line sync signal according to the correction signal in the sub scanning direction from the correction unit 104 based on the reference line sync signal ( Lsync ) output from the control unit 100. A line sync signal (Lsync) in which the output interval (cycle) is corrected in the positive direction or the negative direction is output.

  In addition, the timing signal generation unit 107 is connected to the control unit 100, the correction unit 104, and the clock signal generation unit 108. The timing signal generator 107 generates the transfer signal CK in synchronization with the corrected line sync signal (Lsync) from the line sync signal correction unit 106 based on the reference clock signal from the reference clock generator 108.

  The timing signal generation unit 107 is connected to the image data development unit 105 and is synchronized with the line sync signal (Lsync) from the line sync signal correction unit 106 based on the reference clock signal from the reference clock generation unit 108. Then, the data write signal WR for writing an image corresponding to each pixel and the data read signal RE for reading an image corresponding to each pixel from the image data development unit are output to the image data development unit 105. Further, the timing signal generation unit 107 is connected to the output unit 109, and individually outputs the trigger signal TRG for starting lighting of the LED array 33 based on the reference clock signal from the reference clock generation unit 108.

The output units 109 _{1 to} 109 ₁₂₈ are connected to the image data development unit 105, the timing signal generation unit 107, and the reference clock generation unit 108. When the image data from the image data development unit 105 is 1, the timing signal generation unit The trigger signal TRG from 107 is output to the LED array 33, and the trigger signal TRG from the timing signal generation unit 107 is not output to the LED array 33 when the image data from the image data development unit 105 is 0. Yes. Then, the output units 109 _{1 to} 109 ₁₂₈ generate lighting pulses having the number of clocks corresponding to the image data, and output them to the LED array 33.

  In FIG. 7, reference numeral 110 denotes a control panel of the image forming apparatus 1. The control panel 110 is connected to the control unit 100.

In this embodiment, as shown in FIG. 4, the plurality of LED elements of the LED array 33 are at least two (plural) (for example, 128) light emitting element groups 120 ₁ along the main scanning direction. ˜120 ₁₂₈ (hereinafter referred to as “small area”). One small region 120 includes a plurality of (for example, 128) LED elements and has a length of about 2.7 mm along the main scanning direction. The LED array 33 is composed of 16384 (= 128 × 128) LED elements as a whole.

  As shown in FIG. 8, the image data development unit 105 includes 128 dual-port RAMs (512 w × 128 pix) 130 corresponding to a plurality of small areas of the LED array 33 as line buffers. As shown in FIG. 9, the dual port RAM 130 decodes the lower 7 bits (A0 to A6) of the address signal output from the correction unit 104 by the decoder 131 and outputs it from the timing signal generation unit 108 via the AND circuit 132. Is combined with the data write signal WR # N to be a data write signal WR # N for each dual port RAM 130. In the dual port RAM 130, image data is written for each suitable number of pixels, such as writing 128 pix (pixels) at a time or adjusting to the previous stage processing by a bit enable function of the memory.

  The dual port RAM 130 is configured to write image data (D0 to D512) for each line along the sub-scanning direction specified by the upper 9 bits (A7 to A15) of the address signal output from the correction unit 104. ing.

  On the writing side of each dual port RAM 130, 128 dual port RAMs 130 are concatenated to form one line with apparently 0 address to 127 addresses as 128 pixel data for each dual port RAM 130, and 128 addresses to 255 addresses. Up to the second line, the 256th address to the 383rd address are the third line, and so on, and the image data is sequentially stored up to the last 512 lines. The dual port RAM 111 is used as a ring buffer, and the maximum correction amount along the sub-scanning direction is up to 512 lines corresponding to the line buffer in the image of one page.

On the other hand, the read side of each dual port RAM 130 is configured to read image data at a different read timing for each dual port RAM 130. Therefore, the timing signal generation unit 107 outputs the data read signal RE to each dual port RAM 130 individually. Image data read from each dual port RAM 130 at individual timings is sent to corresponding output units 109 _{1 to} 109 ₁₂₈ , respectively.

  In this embodiment, the data read signal RE output to each dual port RAM 130 and the output timing of the data read signal RE are corrected in the sub scanning direction output from the correction unit 104 to the line sync signal correction unit 106. It has been changed by.

The data read signal RE and the data read signal RE output to each dual port RAM 130 are synchronized with the reference line sync signal ( Lsync ) output from the control unit 100 to the line sync signal correction unit 106 in a state before correction. Is output.

On the other hand, the correction unit 104 outputs a correction signal in the sub-scanning direction to the line sync signal correction unit 106. Then, as shown in FIG. 10, the line sync signal correction unit 106 sets the output interval (cycle) of the output line sync signal (Lsync) in accordance with the correction signal in the sub-scanning direction. The sync signal ( Lsync ) is corrected to a different value. The timing signal generator 107 changes the output timing of the data read signal RE and the data read signal RE output to each dual port RAM 130 based on the line sync signal (Lsync) output from the line sync signal correction unit 106. As a result, the timing for performing image exposure on the peripheral surface of the photosensitive drum 11 is varied for each of the small regions 120 _{1 to} 120 ₁₂₈ of the LED array 33. As a result, the LED array 33 can correct the image exposure position along the circumferential direction of the photosensitive drum 11 for each of the small regions 120 _{1 to} 120 ₁₂₈ .

<Operation of Characteristic Part of Image Forming Apparatus>
In the image forming apparatus 1 according to this embodiment, a test chart 140 as shown in FIG. 11 is used at a required timing such as when an image is printed on a predetermined number of recording sheets 5 at the start of use of the apparatus. Is output. The test chart 140 includes a grid-like image in which linear images are formed at predetermined intervals along the main scanning direction and the sub-scanning direction. As the image of the test chart 140, any image can be used as long as distortion of the image can be detected. Moreover, the color of the image of the test chart 140 is arbitrary, and for example, a black (K) color image is used.

  In the image forming apparatus 1, when an image is formed on the recording paper 5, as shown in FIG. In some cases, an image as shown in FIG. 11 (a) is not formed, and a test chart 140 ′ with distortion is output as shown in FIG. 11 (b).

  The output test chart 140 ′ is read by the image reading device 3 of its own device or an image reading device or scanner of another device, and as shown in FIG. 7, the image data of the read test chart 140 ′ is read. Input to the image distortion detection unit 102. The image distortion detection unit 102 detects image distortion along the main scanning direction and the sub-scanning direction from the image data of the test chart 140 ′.

  In the illustrated example, the image of the test chart 140 ′ has no image distortion (positional deviation) along the main scanning direction, and only image distortion (positional deviation) along the sub-scanning direction has occurred. Yes. Further, the distortion of the image along the sub-scanning direction is not constant along the main scanning direction, and the distortion amount of the image along the sub-scanning direction differs at a position in the main scanning direction. Yes. The image distortion detection unit 102 detects the distortion amount of the image along the sub-scanning direction at such a position in the main scanning direction.

The distortion amount of the image detected by the image distortion detection unit 102 is sent to the correction value calculation unit 103, and the correction value calculation unit 103 is based on a correction value calculation formula that is predetermined to correct the distortion amount of the image. A correction value is calculated. At that time, the correction value calculation unit 103 calculates a correction value using 128 pixels corresponding to each small region 120 of the LED array 33 as one correction unit along the main scanning direction. As the correction value, the time for increasing or decreasing the output interval (cycle) of the line sync signal ( Lsync ) with respect to the reference line sync signal ( Lsync ) for each of the small areas 120 _{1 to} 120 ₁₂₈ of the LED array 33 is photosensitive. Calculation is made according to the process speed, which is the rotational speed of the body drum 11.

More specifically, the test chart 140 ′ shown in FIG. 11 has image distortion that occurs when each of the small areas 120 _{1 to} 120 ₁₂₈ of the LED array 33 is driven by a reference line sync signal ( Lsync ). Yes. Therefore, the correction value calculation unit 103 compares the image interval along the sub-scanning direction with the original interval in order to correct the test chart 140 ′ shown in FIG. The narrower region 120 is corrected so that the output interval (cycle) of the line sync signal ( Lsync ) is longer than the reference line sync signal ( Lsync ). In addition, for a small region 120 where the image interval along the sub-scanning direction is wider than the original interval, the output interval (cycle) of the line sync signal ( Lsync ) is shorter than the reference line sync signal ( Lsync ). Correct so that

The correction value calculated by the correction value calculation unit 103 is input to the correction unit 104. The correction unit 104 divides the image data from the image processing unit 101 along the main scanning direction corresponding to the small regions 120 _{1 to} 120 ₁₂₈ of the LED array 33, and the divided image data of the image data development unit 105. Write to the corresponding dual port RAM 130 ₁ -130 ₁₂₈ .

At this time, the writing timing of the image data to each of the dual port RAMs 130 _{1 to} 130 ₁₂₈ is determined by the data writing signal WR output from the timing signal generator 107. The data write signal WR is corrected for each unit determined in advance in the plus direction or the minus direction with respect to the reference period with the period of the reference line sync signal set to “0”.

Further, the read timing of image data from each of the dual port RAMs 130 _{1 to} 130 ₁₂₈ is determined by the data read signal RE output from the timing signal generator 107. The data read signal WR is also corrected for each unit predetermined in the plus direction or the minus direction with respect to the reference period with the period of the reference line sync signal set to “0”.

The data write signal WR and the data read signal RE output to each of the dual port RAMs 130 _{1 to} 130 ₁₂₈ generate timing signals corresponding to the small areas 120 _{1 to} 120 ₁₂₈ of the LED array 33 from the line sync signal correction unit 106. Correction is performed based on the output interval (cycle) of the line sync signal (Lsync) output to the unit 107.

FIG. 13 is a chart showing an example of a state in which the data write signal WR and the data read signal RE output to each of the dual port RAMs 130 _{1 to} 130 ₁₂₈ are corrected.

Since the first line of the LED array 33 is lit, the correction values of the data write signal WR and the data read signal RE output to the dual port RAMs 130 _{1 to} 130 ₁₂₈ are all “0”. The correction values of the data write signal WR for the second and subsequent lines are “−1”, “−2”, “−2”,..., And for all the dual port RAMs 130 _{1 to} 130 ₁₂₈ . It is common.

On the other hand, the correction values of the data read signal RE for the second and subsequent lines are “0”, “0”, “0”, “0”, “0”, “0”, “0” for the _first dual-port RAM 1301. , “0”, “−1”,..., And the 128th dual port RAM 130 ₁ is “0”, “0”, “0”, “0”, “0”, “0”. , “0”, “0”, “+1”,...

Correction value has been read timing synthesis in the dual port RAM 130 ₁ to 130 DEG ₁₂₈ is a value obtained by adding the correction value of the correction value and the data read signal RE of the data write signal WR, 1 th dual port RAM 130 ₁ is " 0 ”,“ −1 ”,“ −2 ”,“ −2 ”,“ −1 ”,“ 0 ”,“ 0 ”,“ 0 ”,..., And the 128th dual port RAM 130 ₁ Becomes “0”, “−1”, “−2”, “−2”, “−1”, “0”, “0”, “0”,.

In this way, in the LED eyelet 33, as shown in FIG. 14, the small area is based on the image data output from the dual port RAMs 130 _{1 to} 130 ₁₂₈ of the image data development unit 105 to the output units 109 _{1 to} 109 _128. The light emission timing of the LED elements is corrected every 120 _{1 to} 120 ₁₂₈ , and image distortion is corrected as shown in FIG. As a result, the image forming apparatus 1 can obtain a test chart 140 in which image distortion is corrected as shown in FIG.

In this embodiment, since it is sufficient to correct the light emission timing for each of the small areas 120 _{1 to} 120 _{128 of the} LED eyelet 33, it is possible to easily correct image distortion even in the LED eyelet 33 having a high resolution. .

  In the image forming apparatus 1, image distortion correction along the main scanning direction is performed by the correction unit 104 moving the pixels along the main scanning direction, or by inserting or thinning out pixels as shown in FIG. 15. As a result, correction is performed as a stage before image data is sent to the image data development unit 105.

In this embodiment, as shown in FIG. 16, when image data is enlarged along the sub-scanning direction, the writing timing and reading timing of the image data with respect to each of the dual port RAMs 130 _{1 to} 130 ₁₂₈ are By changing the data according to the enlargement cycle along the sub-scanning direction, the amount of image data stored per unit time in each of the dual port RAMs 130 _{1 to} 130 ₁₂₈ can be reduced. _{1 to} 130 ₁₂₈ can be used effectively.

  Note that image distortion correction along the main scanning direction may lead to degradation of image quality due to pixel insertion or thinning, and therefore, as described in Japanese Patent No. 4003803, image information using random numbers is used. It is desirable to perform a process for determining a pixel to be corrected in each area.

[Embodiment 2]
FIG. 17 shows a main part of the image forming apparatus according to the second embodiment.

  The control panel 110 of the image forming apparatus 1 includes a touch panel 111 that also serves as a display unit that displays an operation menu, a warning, a message, and the like to the user and receives various settings for the displayed operation menu, and a plurality of operation buttons 112. Yes. As shown in FIG. 17, the touch panel 111 shows a typical image distortion state 150 that occurs in an image output to the recording paper 5 as image distortion correction.

  The user operates the touch panel 111 of the control panel 110 to select the image distortion state 150 to be corrected. At this time, the touch panel 111 has image distortion levels (levels) 151 along the main scanning direction and the sub-scanning direction set to “+1”, “+2”, “+3”,... “−1”, “−2”. ”,“ −3 ”,... May be configured to be set together numerically.

  As shown in FIG. 7, the control unit 100 is configured to output a correction signal to the correction unit 104 according to the state 150 and level of the image distortion to be corrected input from the touch panel 111 of the control panel 110. Has been.

  In the second embodiment, the user can easily correct the distortion of the image printed on the recording paper 5 by operating the control panel 110 without printing the test chart 140.

  In the above-described embodiment, the case of correcting image distortion in which the amount of displacement is different in the main scanning direction along the sub-scanning direction has been described. However, the present invention is not limited to this. By changing the writing time and the reading time, it is possible to correct the AC component along the sub-scanning direction by using the print start reference along the sub-scanning direction. It is also possible to correct misalignment between the image and the back side image.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2 ... Image forming part 3 ... Image reading apparatus 11 ... Photosensitive drum 13 ... Exposure apparatus 14 ... Developing apparatus 33 ... LED array 36 ... Drive apparatus 100 ... Control part 101 ... Image processing part 102 ... Image distortion detection Unit 103 ... Correction value calculation unit 104 ... Correction unit 105 ... Image data development unit 106 ... Line sync signal correction unit 107 ... Timing signal generation unit 108 ... Reference clock generation unit 109 ... Output unit 130 ... Dual port RAM

Claims (7)

A photoconductor rotatably provided around a rotation axis;
A plurality of light emitting elements arranged along the direction of the rotation axis, and exposure means for performing exposure by causing the plurality of light emitting elements to emit light to the photoconductor;
A plurality of storage means for storing image data for causing the light emitting elements to emit light for each of at least two light emitting element groups arranged in the direction of the rotation axis among the plurality of light emitting elements;
With
An image forming apparatus, wherein a light emission interval on the photoconductor is changed for each of the light emitting element groups by changing a reading cycle for reading the image data from the plurality of storage units.   The image forming apparatus according to claim 1, wherein the plurality of storage units include a dual port RAM having ports on a writing side and a reading side of image information.   The plurality of dual port RAMs are arranged along the direction of the rotation axis, and writing to each dual port RAM is performed continuously for one line, and reading from each dual port RAM is performed by the exposure means. The image forming apparatus according to claim 2, which is performed for each light emitting element group.   Correction information generation means for generating correction information of an image along the rotation direction of the photoconductor in the axial direction, and the plurality of dual port RAMs based on the correction information generated by the correction information generation means, 4. The image forming apparatus according to claim 2, wherein both the writing time and the reading time of the image information are changed.   5. The light emission interval on the photosensitive member is changed by changing the image information in units of pixels along the axial direction based on correction information generated by the correction information generation unit. The image forming apparatus described in 1.   6. The correction information generation unit according to claim 4, wherein the correction information generation unit generates correction information based on image information obtained by reading a predetermined image distortion detection image output from the image forming apparatus. Image forming apparatus.   The image forming apparatus according to claim 4, wherein the correction information generation unit generates correction information by a user selecting from a plurality of predetermined correction information.

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