JP2008087196A - Optical head driving method, optical head control system, exposure system, and image forming system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend the life of an optical head by shifting allotment of effective light emitting elements and uniformly distributing the degree of deterioration of the light emitting elements. <P>SOLUTION: In an optical head driving method, a control circuit 22 generates a control signal CTL. A dummy data adding circuit 21 adds dummy data Dd to input image data Din according to the control signal CTL to generate output image data Dout. When the same image is continuously printed and the image data includes a line of a predetermined length along a sheet conveying direction, the control circuit 22 generates the control signal CTL so as to shift the effective light emitting elements by a predetermined number of light emitting elements corresponding to the width of the line. Thus the light emitting elements that continuously emit light are distributed, therefore, the life of the optical head 1 is extended. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for extending the life of an optical head using a light emitting element.

  A printer as an image forming apparatus uses a light emitting device in which a large number of light emitting elements are arranged in an array as a head unit for forming an electrostatic latent image on an image carrier such as a photosensitive drum. The head portion is often composed of a single line in which a plurality of light emitting elements are arranged along the main scanning direction. In addition, as a light emitting element, a light emitting diode such as an organic light emitting diode (hereinafter simply referred to as “OLED”) element is known.

This light-emitting element has the property that when light is emitted over a long period of time, the characteristics deteriorate and the amount of light decreases. In order to solve this problem, Patent Document 1 discloses a technique that compensates for deterioration of characteristics by detecting the degree of deterioration of the light emitting element and adjusting the drive current supplied to the light emitting element according to the degree of deterioration. It is disclosed.
JP 2003-280581 A

By the way, the deterioration rate of the light emitting element increases as the driving current is increased. For this reason, when the drive current is increased in accordance with the degree of deterioration, the light emitting element is further deteriorated and the life is shortened. As a result, there is a problem that the life of the optical head is shortened. Further, since it is necessary to detect the degree of deterioration, there is a problem that the circuit scale increases.
The present invention has been made in view of such circumstances, and uses an optical head driving method, an optical head control device, an exposure device, and an optical head that can extend the life of the optical head with a simple configuration. It is an object of the present invention to provide an image forming apparatus.

  In order to solve this problem, an optical head driving method according to the present invention includes a plurality of light emitting elements arranged in one direction, and among the plurality of light emitting elements, a continuous number corresponding to the width of a sheet to be printed. The light emitting element disposed as an effective light emitting element, and a method of driving an optical head that performs exposure using the effective light emitting element, between the printing of one sheet and the printing of the next sheet, The allocation of light emitting elements to be used as the effective light emitting elements among the plurality of light emitting elements is shifted.

  According to the present invention, the optical head includes a light emitting element exceeding the width of the paper. Then, exposure is performed using effective light emitting elements assigned to some of the plurality of light emitting elements, but the allocation of effective light emitting elements is shifted between a certain sheet and the next sheet. A series of identical images is often performed. For this reason, when the effective light emitting element is fixed, the deterioration occurs in variation. However, if the allocation of the effective light emitting element is shifted as in the present invention, the degree of deterioration can be dispersed. As a result, the deterioration of a specific light-emitting element among the plurality of light-emitting elements does not proceed and the life of the entire optical head is not shortened, and the life can be extended.

  In another aspect of the optical head driving method according to the present invention, the optical head includes a plurality of light emitting elements arranged in one direction, and the number of the light emitting elements is continuous according to the width of the paper to be printed. A method for driving an optical head that performs exposure using the effective light emitting element as an effective light emitting element, and determines whether or not the same image is continuously printed on a plurality of sheets. When it is determined that printing is performed continuously, a light emitting element used as the effective light emitting element among the plurality of light emitting elements during printing of a certain sheet and during printing of the next sheet in a continuous printing period It is characterized by shifting the allocation of. According to the present invention, the allocation of effective light emitting elements is shifted during continuous printing of the same image. If different images are sequentially printed on a plurality of sheets, the deterioration of the light emitting elements is dispersed even if the allocation of the effective light emitting elements is fixed. Therefore, it is possible to shift the allocation of the effective light emitting elements only when the dispersion of deterioration is necessary.

  In another aspect of the optical head driving method according to the present invention, the optical head includes a plurality of light emitting elements arranged in one direction, and the number of the light emitting elements is continuous according to the width of the paper to be printed. A method of driving an optical head that performs exposure using the effective light emitting element as an effective light emitting element, and prints the same image continuously on a plurality of sheets and should be printed In the same image, it is determined whether or not there is a line longer than a predetermined length in the sheet conveyance direction, and when the determination condition is affirmed, during the continuous printing period, printing of a certain sheet and printing of the next sheet The allocation of light emitting elements to be used as the effective light emitting elements among the plurality of light emitting elements is shifted with time. Deterioration of the light emitting element is particularly problematic when a line is drawn in the paper transport direction. According to the present invention, it is possible to detect such a case and change the allocation of effective light emitting elements.

  In another aspect of the optical head driving method according to the present invention, the optical head includes a plurality of light emitting elements arranged in one direction, and the number of the light emitting elements is continuous according to the width of the paper to be printed. A method of driving an optical head that performs exposure using the effective light emitting element as an effective light emitting element, and prints the same image continuously on a plurality of sheets and should be printed In the same image, it is determined whether or not there is a line having a predetermined length or more in the paper conveyance direction, and when the determination condition is affirmed, the width of the line is specified, and during a continuous printing period, Between the printing time and the printing time of the next sheet, the allocation of the light emitting elements to be used as the effective light emitting elements among the plurality of light emitting elements is shifted by the number of the light emitting elements according to the specified line width. It is characterized by that. According to the present invention, the line width is specified, and the allocation of the effective light emitting elements is shifted by the number of the light emitting elements corresponding to the specified line width, so that the light emitting elements that continuously emit light can be more reliably dispersed. It becomes possible.

  The control apparatus for an optical head according to the present invention includes a plurality of light emitting elements arranged in one direction, and controls the light emission states of the plurality of light emitting elements based on output image data indicating gradations of the plurality of light emitting elements. Among the plurality of light emitting elements, light emitting elements that are continuously arranged according to the width of the paper to be printed are used as effective light emitting elements, and an optical head that performs exposure is controlled using the effective light emitting elements. An apparatus that selects one of input image data indicating gradations of a plurality of effective light emitting elements and dummy data indicating gradations not contributing to exposure, and outputs an image indicating gradations of the plurality of light emitting elements Light emission to be used as the effective light-emitting element among the plurality of light-emitting elements between the selection means for generating data (for example, 21 shown in FIG. 4) and the time of printing a certain sheet and the next sheet The element assignments are off In, and a control means for controlling the period in which the selection means selects the input image data (e.g., 22 according to FIG. 4).

  According to the present invention, since the input image data and the dummy data are selected to generate the output image data, the allocation of the effective light emitting elements can be changed depending on the timing at which the input image data is selected. For this reason, it is not necessary to switch the wiring for supplying the drive signal to the light emitting element. In addition, since the light emitting elements used as the effective light emitting elements among the plurality of light emitting elements are controlled to be shifted between the printing time of a certain sheet and the printing time of the next sheet, the degree of deterioration can be dispersed. . As a result, the deterioration of a specific light-emitting element among the plurality of light-emitting elements does not proceed and the life of the entire optical head is not shortened, and the life can be extended.

  In the above-described optical head control device, as a specific aspect of the control means, it is determined whether or not the same image is continuously printed on a plurality of sheets. In the period of time, the selection means inputs the input so that the assignment of light emitting elements to be used as the effective light emitting elements out of the plurality of light emitting elements is shifted between printing of a certain sheet and printing of the next sheet. It is preferable to control the period for selecting image data. According to the present invention, the allocation of effective light emitting elements is shifted during continuous printing of the same image. If different images are sequentially printed on a plurality of sheets, the deterioration of the light emitting elements is dispersed even if the allocation of the effective light emitting elements is fixed. Therefore, the allocation of effective light emitting elements can be shifted only when degradation dispersion is required.

  In the optical head control device described above, as a specific aspect of the control means, the same image is continuously printed on a plurality of sheets, and a predetermined length in the sheet conveyance direction in the same image to be printed. If it is determined whether or not the above line is present and the determination condition is affirmed, during the continuous printing period, between the time of printing a certain sheet and the time of printing the next sheet, It is preferable to control a period during which the selection unit selects the input image data so that assignment of light emitting elements to be used as the effective light emitting elements is shifted. Deterioration of the light emitting element is particularly problematic when a line is drawn in the paper transport direction. According to the present invention, it is possible to detect such a case and change the allocation of effective light emitting elements.

  In the above-described optical head control device, the control unit continuously prints the same image on a plurality of sheets, and the same image to be printed has a line having a predetermined length or more in the sheet conveyance direction. If the determination condition is affirmative, the width of the line is specified, and the plurality of light emission is performed during printing of a certain sheet and during printing of the next sheet in a continuous printing period. The selection means controls the period for selecting the input image data so that the allocation of the light emitting elements to be used as the effective light emitting elements among the elements is shifted by the number of the light emitting elements according to the specified line width. It is preferable. According to the present invention, the line width is specified, and the allocation of the effective light emitting elements is shifted by the number of the light emitting elements corresponding to the specified line width, so that the light emitting elements that continuously emit light can be more reliably dispersed. It becomes possible.

  Next, an exposure apparatus according to the present invention includes a plurality of light emitting elements arranged in one direction, and among the plurality of light emitting elements, a number of light emitting elements that are continuously arranged according to the width of a sheet to be printed are arranged. An effective light-emitting element includes an optical head that performs exposure using the effective light-emitting element, and the above-described optical head control device. According to this exposure apparatus, the deterioration of the light emitting element can be dispersed, so that the life of the optical head can be extended, and as a result, the life of the entire exposure apparatus can be extended.

  Next, an image forming apparatus of the present invention includes the above-described exposure apparatus and an image carrier on which an image is formed by light irradiated from the optical head. A typical example of such an image forming apparatus is a printer, which includes a copying machine, a facsimile machine, a multifunction machine, and the like.

A preferred embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure.
<1. Embodiment>
FIG. 1 is a perspective view illustrating a partial configuration of an image forming apparatus using an optical head according to an embodiment. As shown in the figure, the image forming apparatus includes an optical head 1, a condensing lens array 15, and a photosensitive drum 110. The optical head 1 has a large number of light emitting elements arranged in an array. These light emitting elements selectively emit light according to an image to be printed on a recording material such as paper. For example, an organic light emitting diode element (hereinafter referred to as an OLED element) is used as the light emitting element. The condensing lens array 15 is disposed between the optical head 1 and the photosensitive drum 110. The condensing lens array 15 includes a large number of gradient index lenses arranged in an array with each optical axis facing the optical head 1. The light emitted from each light emitting element of the optical head 1 passes through each gradient index lens of the condensing lens array 15 and reaches the surface of the photosensitive drum 110. By this exposure, a latent image corresponding to a desired image is formed on the surface of the photosensitive drum 110.

  FIG. 2 is a plan view showing the configuration of the optical head 1. In the optical head 1 of this example, x (= n + m) light emitting elements P (P1 to Px) are arranged in one direction. However, x, n, and m are natural numbers. As will be described later, the optical head 1 includes various circuits and memories for driving the light emitting element P, but is omitted for convenience of description. In the present embodiment, among the x light emitting elements P, n light emitting elements P are used for actual exposure, and the remaining m light emitting elements P are not used. In the following description, the light emitting element P used for exposure is referred to as an effective light emitting element Pv, and the light emitting element P that is not used for exposure is referred to as a dummy light emitting element Pd.

  That is, in order to print a sheet having a predetermined width, n light emitting elements P are originally necessary, but the optical head 1 includes m light emitting elements P. Which of the x light emitting elements P is assigned to the effective light emitting element Pv is determined according to the printing situation.

  For example, in the example shown in FIG. 3A, the effective light emitting element Pv is assigned to n light emitting elements P from the left end. In this case, the light emitting element P indicated by a black circle emits light and draws a line having a width L in the paper conveyance direction. When this image is continuously printed, the light emitting element P indicated by the black circle emits light over a long period of time, so that the deterioration is faster than the other light emitting elements P. Therefore, when the next sheet is printed, the allocation of the effective light emitting elements Pv is shifted. For example, as shown in FIG. 3B, dummy light emitting elements Pd are assigned to the third light emitting elements P from the left end, and effective light emitting elements Pv are assigned to the fourth to 3 + n light emitting elements P. Thereby, the light emission time can be dispersed in each light emitting element P.

  FIG. 4 shows a block diagram of an exposure apparatus 100 using the optical head 1. The exposure apparatus 100 includes a head control circuit 2 that controls the optical head 1. The optical head 1 includes a print data writing circuit 11 and a drive circuit 12. The print data writing circuit 11 functions as an interface for supplying the output image data Dout supplied from the head control circuit 2 to the drive circuit 12. The drive circuit 12 supplies a drive current corresponding to the gradation to the x light emitting elements P1 to Px based on the output image data Dout. The light emission power of each light emitting element P1 to Px is determined by the product of luminous intensity and light emission time. Therefore, the light emission power corresponding to the gradation may be output by adjusting the magnitude of the drive current with the light emission time constant, or the light emission time is adjusted with the magnitude of the drive current constant. Accordingly, the light emission power corresponding to the gradation may be output.

Next, the head control circuit 2 includes a buffer 20, a dummy data addition circuit 21, and a control circuit 22. The head control circuit 2 is supplied with print data Dg from the host device. The print data Dg includes input image data Din and attribute data Dz. The input image data Din indicates the gradation to be displayed by each of the n effective light emitting elements Pv. The attribute data Dz indicates information accompanying printing such as the number of continuous prints and the paper orientation.
When receiving the print data Dg, the control circuit 22 stores the input image data Din in the buffer 20, while generating the control signal CTL for analyzing the attribute data Dz and the input image data Din and controlling the dummy data adding circuit 21. . Although detailed processing will be described later, it is controlled where the effective light emitting element Pv is allocated to the plurality of light emitting elements P. The buffer 20 can store the input image data Din, and is configured to control the read timing and read speed.

  The dummy data adding circuit 21 adds the dummy data Dd to the input image data Din read from the buffer 20 to generate output image data Dout. The dummy data Dd indicates the gradation of the dummy light emitting element Pd, and a gradation that does not contribute to exposure is set. In this example, it is “0”. The control signal CTL instructs a period for selecting the input image data Din and a period for selecting the dummy data Dd, and the dummy data adding circuit 21 generates the output image data Dout according to the control signal CTL.

  FIG. 5 is a flowchart showing the contents of the generation process of the control signal CTL. The control circuit 22 determines whether or not the same image is continuously printed based on the attribute data Dz (step S1). If it is not continuous printing, the allocation of the effective light emitting elements Pv is not changed (step S2). In this case, the control signal CTL is generated so that the effective light emitting element Pv is assigned to the light emitting element P that is initially set. For example, the control signal CTL is generated so that the effective area to which the effective light emitting element Pv is allocated is arranged left-justified in the x light emitting elements P1 to Px.

  On the other hand, if the same image is continuously printed and the determination condition in step S1 is affirmed, the control circuit 22 determines whether or not there is a line having a predetermined length in the paper transport direction (step S3). More specifically, the control circuit 22 performs the following processing. First, input image data Din for which continuous printing is designated is read from the buffer 20, and binarized by comparison with a predetermined reference value. Here, the predetermined reference value is selected as a value that causes deterioration of the light emitting element P when a line having a predetermined length is drawn. For example, 100% black may be set as a reference value, and binarized so that “1” is set when the input image data Din is a value indicating 100% black, and “0” is set when other values are set. . Secondly, it is determined whether or not dots of a reference value or more continue in the paper conveyance direction for a predetermined length or more. If this determination condition is affirmed, the line is determined to be a line.

  If the determination condition in step S3 is negative, the control circuit 22 advances the process to step S2 described above, and does not change the allocation of the effective light emitting elements Pv. On the other hand, if the determination condition is affirmed, the line width is specified (step S4). Thereafter, the control circuit 22 selects a light-emitting element P to be used as an effective light-emitting element Pv among the plurality of light-emitting elements P between the time of printing a certain sheet and the time of printing the next sheet in a continuous printing period. A control signal CTL is generated so as to be shifted by the number of light emitting elements P corresponding to the specified line width (step S5). Here, the continuous number of the light emitting elements P that is “1” as a result of the binarization in the above-described step S3 corresponds to the line width.

Here, it is assumed that four identical images including a line having a width of “3” are continuously printed. In this case, the output image data Dout is as shown in FIG. 6, and the allocation of the effective light emitting elements Pv is as shown in FIG. The first output image data Dout has n pieces of input image data Din arranged from the top. For this reason, the effective light emitting elements Pv are assigned to n from the left end. In the second output image data Dout, three pieces of dummy data Dd are inserted from the top, followed by n pieces of input image data Din. For this reason, the effective light emitting elements Pv are allocated to n elements from the fourth light emitting element P from the left end. In the third output image data Dout, dummy data Dd is inserted into six pieces from the head, and subsequently n pieces of input image data Din are arranged. For this reason, the effective light emitting elements Pv are allocated to n elements from the seventh light emitting element P from the left end. In the fourth output image data Dout, dummy data Dd is inserted into the nine pieces from the head, and n pieces of input image data Din are subsequently arranged. For this reason, the effective light emitting elements Pv are assigned to n elements from the tenth light emitting element P from the left end.
As a result, the light emitting element P that draws a line of width “3” moves by three dots as indicated by a black circle in FIG. Thereby, the light emitting elements P that emit light continuously can be dispersed, and the life of the optical head 1 can be extended.

<2. Modification>
The present invention is not limited to the above-described embodiments, and for example, the following modifications are possible.
(1) In the above-described embodiment, the effective area to which the effective light emitting element Pv is allocated is shifted by the line width on the condition that the line is continuously printed and the line exists. However, the shift amount is not necessarily equal to the line width. The shift amount may be determined according to the line width. For example, when the line width is “1” to “3”, the shift amount is “3”, when the line width is “4” to “6”, the shift amount is “6”, and the line width is “7”. When it is above, the shift amount may be “8”.

(2) In the above-described embodiment, the shift amount is sequentially increased. However, the shift amount may be decreased when reaching a predetermined value, and the increase and decrease may be repeated. For example, when the line width is “3”, the shift amount is “0” → “3” → “6” → “9” → “6” → “3” → “0” → “3” →. May be changed.

(3) Further, the assignment of the effective light emitting elements Pv may be changed only on the condition that continuous printing is performed. FIG. 8 shows the content of the generation process of the control signal CTL according to the modification. In this case, in the case of continuous printing, the control circuit 22 generates the control signal CTL so as to shift the allocation of the effective light emitting elements Pv by a predetermined number (step S6). Here, the predetermined number is a predetermined fixed number. In this case, since there is no need to detect the presence of a line, the length of the line, and the line width, the processing can be greatly simplified. Here, it is assumed that four identical images including a line having a predetermined number “2” and a width “3” are continuously printed. FIG. 9 shows how the effective light emitting elements Pv are assigned. In this case, since the shift amount is “2”, the fourth, sixth, and eighth light emitting elements P emit light over two pages, but light is emitted continuously for four pages. Can be prevented.

(4) Furthermore, the control circuit 22 shifts the allocation of the effective light emitting elements by a predetermined number between printing of a certain sheet and printing of the next sheet, without determining that the same image is continuously printed. Alternatively, the control signal CTL may be generated. In this case, the processing can be further simplified.

(5) In the above-described embodiment, an OLED element has been described as an example of an electro-optical element whose optical characteristics change depending on electric energy. However, the present invention is not limited to this, for example, a field emission element ( A light emitting element such as an FED), a surface conduction type emission element (SED), or a ballistic electron emission element (BSD) may be used.

<3. Image forming apparatus>
As shown in FIG. 1, the optical head 1 according to the embodiment can be used as a line-type optical head for writing a latent image on an image carrier in an image forming apparatus using an electrophotographic system. Examples of the image forming apparatus include a printer, a printing part of a copying machine, and a printing part of a facsimile.
FIG. 10 is a longitudinal sectional view showing an example of an image forming apparatus using the optical head 1. This image forming apparatus is a tandem type full color image forming apparatus using a belt intermediate transfer body system.

  In this image forming apparatus, four organic EL array exposure heads 1K, 1C, 1M, and 1Y having the same configuration have four photosensitive drums (image carriers) 110K, 110C, 110M, and 110Y having the same configuration. The exposure positions are respectively arranged. The organic EL array exposure heads 1K, 1C, 1M, and 1Y are the optical head 1 exemplified in the embodiment.

  As shown in FIG. 10, this image forming apparatus is provided with a driving roller 121 and a driven roller 122. An endless intermediate transfer belt 120 is wound around these rollers 121 and 122, and an arrow indicates. As shown, the periphery of the rollers 121 and 122 is rotated. Although not shown, tension applying means such as a tension roller that applies tension to the intermediate transfer belt 120 may be provided.

  Around the intermediate transfer belt 120, four photosensitive drums 110K, 110C, 110M, and 110Y each having a photosensitive layer on the outer peripheral surface are arranged at a predetermined interval. The subscripts K, C, M, and Y mean that they are used to form black, cyan, magenta, and yellow visible images, respectively. The same applies to other members. The photosensitive drums 110K, 110C, 110M, and 110Y are rotationally driven in synchronization with the driving of the intermediate transfer belt 120.

  Around each photosensitive drum 110 (K, C, M, Y), a corona charger 111 (K, C, M, Y), an organic EL array exposure head 1 (K, C, M, Y), and Developers 114 (K, C, M, Y) are disposed. The corona charger 111 (K, C, M, Y) uniformly charges the outer peripheral surface of the corresponding photosensitive drum 110 (K, C, M, Y). The organic EL array exposure head 1 (K, C, M, Y) writes an electrostatic latent image on the charged outer peripheral surface of the photosensitive drum. Each organic EL array exposure head 1 (K, C, M, Y) is arranged such that the arrangement direction of the plurality of light emitting elements P is along the bus (main scanning direction) of the photosensitive drum 110 (K, C, M, Y). Installed. The electrostatic latent image is written by irradiating the photosensitive drum 110 with light by the plurality of effective light emitting elements Pv. The developing device 114 (K, C, M, Y) forms a visible image, that is, a visible image on the photosensitive drum by attaching toner as a developer to the electrostatic latent image.

  The black, cyan, magenta, and yellow developed images formed by the four-color single-color image forming station are sequentially transferred onto the intermediate transfer belt 120 to be superimposed on the intermediate transfer belt 120. As a result, a full-color image is obtained. Four primary transfer corotrons (transfer devices) 112 (K, C, M, Y) are arranged inside the intermediate transfer belt 120. The primary transfer corotron 112 (K, C, M, Y) is disposed in the vicinity of the photosensitive drum 110 (K, C, M, Y), and the photosensitive drum 110 (K, C, M, Y). The electrostatic image is electrostatically attracted from the toner image to transfer the visible image to the intermediate transfer belt 120 passing between the photosensitive drum and the primary transfer corotron.

  A sheet 102 as an object on which an image is to be finally formed is fed one by one from the sheet feeding cassette 101 by the pickup roller 103, and between the intermediate transfer belt 120 and the secondary transfer roller 126 in contact with the driving roller 121. Sent to the nip. The full-color visible image on the intermediate transfer belt 120 is secondarily transferred to one side of the sheet 102 by the secondary transfer roller 126 and fixed on the sheet 102 through the fixing roller pair 127 as a fixing unit. . Thereafter, the sheet 102 is discharged onto a paper discharge cassette formed in the upper part of the apparatus by a paper discharge roller pair 128.

Next, another embodiment of the image forming apparatus according to the present invention will be described.
FIG. 11 is a longitudinal sectional view of another image forming apparatus using the optical head 1. This image forming apparatus is a rotary developing type full-color image forming apparatus using a belt intermediate transfer body system. In the image forming apparatus shown in FIG. 11, a corona charger 168, a rotary developing unit 161, an organic EL array exposure head 167, and an intermediate transfer belt 169 are provided around the photosensitive drum 165.

  The corona charger 168 uniformly charges the outer peripheral surface of the photosensitive drum 165. The organic EL array exposure head 167 writes an electrostatic latent image on the charged outer peripheral surface of the photosensitive drum 165. The organic EL array exposure head 167 is the optical head 1 of each aspect exemplified above, and is installed such that the arrangement direction of the plurality of light emitting elements 30 is along the bus line (main scanning direction) of the photosensitive drum 165. The electrostatic latent image is written by irradiating the photosensitive drum 165 with light from these light emitting elements 30.

  The developing unit 161 is a drum in which four developing units 163Y, 163C, 163M, and 163K are arranged at an angular interval of 90 °, and can rotate counterclockwise about the shaft 161a. The developing units 163Y, 163C, 163M, and 163K supply yellow, cyan, magenta, and black toners to the photosensitive drum 165, respectively, and attach the toner as a developer to the electrostatic latent image, thereby the photosensitive drum 165. A visible image, that is, a visible image is formed.

  The endless intermediate transfer belt 169 is wound around a driving roller 170a, a driven roller 170b, a primary transfer roller 166, and a tension roller, and is rotated around these rollers in a direction indicated by an arrow. The primary transfer roller 166 transfers the visible image to the intermediate transfer belt 169 that passes between the photosensitive drum and the primary transfer roller 166 by electrostatically attracting the visible image from the photosensitive drum 165.

  Specifically, in the first rotation of the photosensitive drum 165, an electrostatic latent image for a yellow (Y) image is written by the exposure head 167, and a developed image of the same color is formed by the developing unit 163Y. The image is transferred to the transfer belt 169. Further, in the next rotation, an electrostatic latent image for a cyan (C) image is written by the exposure head 167, and a developed image of the same color is formed by the developing device 163C. The intermediate transfer is performed so as to overlap the yellow developed image. Transferred to the belt 169. Then, during the four rotations of the photosensitive drum 165, yellow, cyan, magenta, and black visible images are sequentially superimposed on the intermediate transfer belt 169. As a result, a full-color visible image is formed on the transfer belt 169. It is formed. When images are finally formed on both sides of a sheet as an object on which an image is to be formed, the same color images of the front and back surfaces are transferred to the intermediate transfer belt 169, and then the front and back surfaces are transferred to the intermediate transfer belt 169. A full-color visible image is obtained on the intermediate transfer belt 169 by transferring the visible image of the next color.

  The image forming apparatus is provided with a sheet conveyance path 174 through which a sheet passes. The sheets are picked up one by one from the paper feed cassette 178 by the pick-up roller 179, advanced through the sheet transport path 174 by the transport roller, and between the intermediate transfer belt 169 and the secondary transfer roller 171 in contact with the drive roller 170a. Pass through the nip. The secondary transfer roller 171 transfers the developed image to one side of the sheet by electrostatically attracting a full-color developed image from the intermediate transfer belt 169 collectively. The secondary transfer roller 171 can be moved closer to and away from the intermediate transfer belt 169 by a clutch (not shown). The secondary transfer roller 171 is brought into contact with the intermediate transfer belt 169 when a full-color visible image is transferred onto the sheet, and is separated from the secondary transfer roller 171 while the visible image is superimposed on the intermediate transfer belt 169.

  The sheet on which the image has been transferred as described above is conveyed to the fixing device 172 and is passed between the heating roller 172a and the pressure roller 172b of the fixing device 172, whereby the visible image on the sheet is fixed. The sheet after the fixing process is drawn into the discharge roller pair 176 and proceeds in the direction of arrow F. In the case of double-sided printing, after most of the sheet passes through the paper discharge roller pair 176, the paper discharge roller pair 176 is rotated in the reverse direction and introduced into the double-sided printing conveyance path 175 as indicated by an arrow G. The Then, the visible image is transferred to the other surface of the sheet by the secondary transfer roller 171, the fixing process is performed again by the fixing device 172, and then the sheet is discharged by the discharge roller pair 176.

Since the image forming apparatus illustrated in FIGS. 10 and 11 uses the light emitting element P as an exposure unit, the apparatus can be made smaller than when a laser scanning optical system is used. It should be noted that the optical head of the present invention can also be used in electrophotographic image forming apparatuses other than those exemplified above. For example, the optical head according to the present invention can be applied to an image forming apparatus that directly transfers a visible image from a photosensitive drum to a sheet without using an intermediate transfer belt, and an image forming apparatus that forms a monochrome image. Is possible.
The optical head according to the present invention is employed in various electronic devices, for example. Examples of such electronic devices include facsimile machines, copiers, multifunction machines, and printers.

1 is a perspective view showing a partial configuration of an image forming apparatus using an optical head 1 according to the present invention. 2 is a plan view showing the configuration of the optical head 1. FIG. It is explanatory drawing which shows an example of the change of allocation of the effective light emitting element Pv. 1 is a block diagram showing a configuration of an exposure apparatus 100. FIG. It is a flowchart which shows the content of the production | generation process of a control signal. It is explanatory drawing which shows an example of output image data. It is explanatory drawing which shows the example of a change of allocation of the effective light emitting element Pv. It is a flowchart which shows the content of the production | generation process of the control signal which concerns on a modification. It is explanatory drawing which shows the example of a change of allocation of the effective light emitting element Pv. 1 is a longitudinal sectional view showing a configuration of an image forming apparatus using an optical head according to the present invention. It is a longitudinal cross-sectional view which shows the other structure of the image forming apparatus using the optical head which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical head, 2 ... Head control circuit, 21 ... Dummy data addition circuit, 22 ... Control circuit, P1-Pn ... Light emitting element, Pv ... Effective light emitting element, Pd ... Dummy light emitting element, 100 ... Exposure equipment.

Claims (10)

A plurality of light emitting elements arranged in one direction, and among the plurality of light emitting elements, a light emitting element continuously arranged by the number corresponding to the width of the paper to be printed is defined as an effective light emitting element, and the effective light emitting element is used. An optical head driving method for performing exposure,
The assignment of light emitting elements to be used as the effective light emitting elements among the plurality of light emitting elements is shifted between printing of a certain sheet and printing of the next sheet.
An optical head driving method characterized by the above. A plurality of light emitting elements arranged in one direction, and among the plurality of light emitting elements, the effective light emitting elements are used as light emitting elements that are continuously arranged according to the width of the paper to be printed. An optical head driving method for performing exposure,
Determine whether to print the same image continuously on multiple sheets,
If it is determined that printing is to be performed continuously, a light emitting element to be used as the effective light emitting element among the plurality of light emitting elements between the time of printing of a certain sheet and the time of printing of the next sheet in a period of continuous printing. Shift the assignment,
An optical head driving method characterized by the above. A plurality of light emitting elements arranged in one direction, and among the plurality of light emitting elements, the effective light emitting elements are used as light emitting elements that are continuously arranged according to the width of the paper to be printed. An optical head driving method for performing exposure,
The same image is continuously printed on a plurality of sheets, and it is determined whether or not there is a line having a predetermined length or more in the sheet conveyance direction in the same image to be printed,
If the determination condition is affirmed, light emitting elements to be used as the effective light emitting elements among the plurality of light emitting elements are allocated between the time of printing a certain sheet and the time of printing the next sheet in a continuous printing period. Shift,
An optical head driving method characterized by the above. A plurality of light emitting elements arranged in one direction, and among the plurality of light emitting elements, the effective light emitting elements are used as light emitting elements that are continuously arranged according to the width of the paper to be printed. An optical head driving method for performing exposure,
The same image is continuously printed on a plurality of sheets, and it is determined whether or not there is a line having a predetermined length or more in the sheet conveyance direction in the same image to be printed,
If the judgment condition is affirmed, specify the width of the line,
In the continuous printing period, the allocation of the light emitting elements to be used as the effective light emitting elements among the plurality of light emitting elements between the printing time of one sheet and the printing time of the next sheet is set to the specified line width. Shift by the number of the corresponding light emitting elements,
An optical head driving method characterized by the above. A plurality of light emitting elements arranged in one direction, and the light emitting states of the plurality of light emitting elements are controlled based on output image data indicating gradations of the plurality of light emitting elements; A control device of an optical head that performs exposure using the effective light emitting element, the light emitting element that is continuously arranged in a number corresponding to the width of the paper,
Selecting means for selecting one of input image data indicating gradations of a plurality of effective light emitting elements and dummy data indicating gradations not contributing to exposure, and generating the output image data;
The selection means selects the input image data so that the assignment of light emitting elements to be used as the effective light emitting elements out of the plurality of light emitting elements is shifted between the printing of a certain sheet and the printing of the next sheet. Control means for controlling the period of time,
An optical head control device. The control means includes
Determine whether to print the same image continuously on multiple sheets,
If it is determined that printing is to be performed continuously, a light emitting element to be used as the effective light emitting element among the plurality of light emitting elements between the time of printing of a certain sheet and the time of printing of the next sheet in a period of continuous printing. Controlling the period during which the selection means selects the input image data so that the assignment is shifted;
6. The optical head control apparatus according to claim 5, wherein The control means includes
The same image is continuously printed on a plurality of sheets, and it is determined whether or not there is a line having a predetermined length or more in the sheet conveyance direction in the same image to be printed,
When the determination condition is affirmed, the light emitting elements to be used as the effective light emitting elements among the plurality of light emitting elements are allocated between the time of printing a certain sheet and the time of printing the next sheet in a continuous printing period. Controlling the period during which the selection means selects the input image data so as to shift,
6. The optical head control apparatus according to claim 5, wherein The control means includes
The same image is continuously printed on a plurality of sheets, and it is determined whether or not there is a line having a predetermined length or more in the sheet conveyance direction in the same image to be printed,
If the judgment condition is affirmed, specify the width of the line,
In the continuous printing period, the allocation of the light emitting elements to be used as the effective light emitting elements among the plurality of light emitting elements between the printing time of one sheet and the printing time of the next sheet is set to the specified line width. Controlling the period during which the selection means selects the input image data so as to deviate by the number of the corresponding light emitting elements.
The control device for an optical head according to claim 5. A plurality of light emitting elements arranged in one direction, and the light emitting states of the plurality of light emitting elements are controlled based on output image data indicating gradations of the plurality of light emitting elements; An optical head that performs light exposure using the effective light emitting elements, and the light emitting elements that are continuously arranged in a number corresponding to the width of the paper,
An optical head control device according to any one of claims 5 to 8,
An exposure apparatus provided. An exposure apparatus according to claim 9,
An image carrier on which an image is formed by light irradiated from the optical head;
An image forming apparatus comprising:

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