JP2007160650A - Optical head, its controlling method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decrease a step difference of a latent image between neighboring blocks. <P>SOLUTION: OLED elements P11-P14 belonging to a block B1 are selected in the order of P11→P12→P13→P14, and the OLED elements P21-P24 belonging to a block B2 adjoining this are selected in the order of P24→P23→P22→P21. As a result of this, the OLED elements P14 and P21 are simultaneously selected. The step difference between the neighboring blocks is solved thereby in the latent image formed on a photoreceptor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical head using a light emitting element, a control method thereof, and an image forming apparatus.

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, an organic light emitting diode (Organic Light Emitting)
A light emitting diode such as a diode (hereinafter abbreviated as “OLED” where appropriate) is known.

The head unit includes, on a substrate, a light emitting diode, a driving current source provided in the vicinity thereof for supplying a driving current to the light emitting diode, and a driving circuit for generating a driving signal for controlling the supply of the driving current. . In such a head portion, a plurality of light emitting diodes are divided into a plurality of blocks, and the light emitting diodes in the blocks are displaced in a direction orthogonal to the arrangement direction, and arranged.
A technique for reversing the direction of displacement between adjacent blocks is disclosed (Patent Document 1).
According to this technique, a step between blocks can be reduced in the latent image formed by the head unit.
JP 2003-80763 A (see FIG. 4)

However, in the conventional head portion, since the light emitting diodes are displaced in the arrangement direction, it is necessary to secure the length of the head portion in a direction orthogonal to the arrangement direction, and there is a problem that the head portion is enlarged. .
Further, since the light emitting diodes are displaced in a certain direction in one block, a sufficient gap cannot be formed between the adjacent light emitting diodes, and there is a restriction in wiring layout.
The present invention has been made in view of such circumstances, and it is an object of the present invention to achieve both reduction in size and improvement in resolution and to facilitate wiring layout.

In order to solve this problem, an optical head according to the present invention drives each light emitting element belonging to a block for each of a plurality of light emitting elements arranged in a straight line and a plurality of blocks obtained by dividing the plurality of light emitting elements. Driving means for generating a drive signal obtained by time-division-multiplexing signals to be performed, and selection means for selectively supplying the drive signal to each light emitting element belonging to the block, the selection means comprising:
In the adjacent blocks, the drive signals are selected so that the light emission order of the light emitting elements is mirror symmetric.
According to the present invention, since the plurality of light emitting elements are arranged in a straight line, the optical head can be miniaturized. In addition, since the drive signal is selected so that the light emission order of the light emitting elements is mirror-symmetric in adjacent blocks, the light emitting elements are arranged at the end of a certain block and at the end of the adjacent block. The light emitting elements can emit light simultaneously. As a result, there is no printing step at the block boundary, and the resolution of the printed image can be improved. Here, the drive signal may be selected so that the light emitting elements in the block emit light sequentially from one end to the other end. In this case, since the printing step in the block can be minimized, the resolution can be further improved.

Another optical head according to the present invention is configured to time-division-multiplex a signal for driving each light-emitting element belonging to a block for each of a plurality of light-emitting elements arranged linearly and a plurality of blocks obtained by dividing the plurality of light-emitting elements. Drive means for generating the drive signal, and selection means for selectively supplying the drive signal to each light emitting element belonging to the block, wherein the selection means has a light emission order of the light emitting elements included in each block. The drive signal is selected so that the order is from the center to the outer end, or from the outer end to the center.
According to the present invention, since the plurality of light emitting elements are arranged in a straight line and the time-division multiplexed drive signal is sequentially supplied to each light emitting element, the latent image formed by this optical head has undulations. The selecting means selects the drive signal so that the light emission order of the light emitting elements included in each block is from the center to the outer end, or from the outer end to the center, so the number of light emitting elements included in one block is determined. By changing it, the waviness period can be made the same, and the print quality can be made equal.

In another optical head according to the present invention, a plurality of light emitting elements are divided into a plurality of blocks, and k (k is a natural number of 2 or more) light emitting elements included in each of the plurality of blocks are parallel to the main scanning direction. k
The k light-emitting elements are arranged on one line and divided into m (m is a natural number of 2 or more) groups, and in each group, the light-emitting elements adjacent in the main scanning direction are divided into m lines. A light-emitting element group disposed in a plurality of blocks, a driving unit that generates a drive signal by time-division-multiplexing a signal for driving each light-emitting element belonging to the block, and k light-emitting elements belonging to the block Selection means for selectively supplying the drive signals in the order of the sub-scanning direction.
According to the present invention, k light-emitting elements are divided into m groups, and in each group,
Since the light emitting elements adjacent to each other in the main scanning direction are arranged for every m lines, a space is created between the light emitting elements, and various wirings can be passed therethrough. K belonging to a block
Since drive signals are selectively supplied to the individual light emitting elements in the order of the sub-scanning direction, the step of the latent image can be minimized.

In another optical head according to the present invention, a plurality of light emitting elements are divided into a plurality of blocks, and k (k is a natural number of 2 or more) light emitting elements included in each of the plurality of blocks are parallel to the main scanning direction. k
A light emitting element group arranged on a line, driving means for generating a drive signal obtained by time-division-multiplexing a signal for driving each light emitting element belonging to the block for each of the plurality of blocks, and k elements belonging to the block Selection means for selectively supplying the drive signals to the light emitting elements in the order of the sub-scanning direction, and the distance E between the lines is defined as F for the print width, K for the number of gradations, and N for a natural number. E = F * (N−1 / K / k).
According to the present invention, k light emitting elements are arranged on k lines parallel to the main scanning direction, and the distance E between the lines is E = F * (N−1 / K / k). Since it is set, the distance E between the lines can be set to the same extent as the print width F by appropriately setting the gradation number K, the light emitting element k included in the block, and the natural number N. Accordingly, a large gap can be formed between the light emitting elements, and it is much easier to pass various wirings between them. Also,
Since the drive signals are selectively supplied to the k light emitting elements belonging to the block in order in the sub-scanning direction, the step of the latent image can be minimized.

Next, an image forming apparatus according to the present invention includes the above-described optical head and an image carrier on which an image is formed by light from the optical head. Examples of the image forming apparatus include a printer, a copying machine, a facsimile machine, and a multifunction machine. In the adjacent block, the drive signal is selected so that the light emission order of the light emitting elements is mirror-symmetric. Therefore, the light emitting element arranged at the end of a certain block and the light emitting element arranged at the end of the adjacent block Can emit light simultaneously. As a result, there is no printing step at the block boundary, and the resolution of the printed image can be improved.

Next, in the optical head control method according to the present invention, in the optical head formed by linearly arranging a plurality of light emitting elements, the plurality of light emitting elements are divided into a plurality of blocks, and A method for controlling the light emission order, comprising: sequentially selecting the light emitting elements in adjacent blocks so that the light emission order is mirror symmetric; and supplying a drive signal to the sequentially selected light emitting elements. To do. According to the present invention, in adjacent blocks,
Since the drive signal is selected so that the light emission order of the light emitting elements is mirror-symmetric, the light emitting elements arranged at the end of a certain block and the light emitting elements arranged at the end of the adjacent block are caused to emit light simultaneously. Can do. As a result, there is no printing step at the block boundary, and the resolution of the printed image can be improved.

Next, in the optical head control method according to the present invention, in the optical head formed by linearly arranging a plurality of light emitting elements, the plurality of light emitting elements are divided into a plurality of blocks, and A method for controlling a light emission order, the step of sequentially selecting the light emitting elements included in each block from the center toward the outer end, or the light emitting elements from the outer end toward the center, and the light emission sequentially selected Providing a drive signal to the device. According to the present invention, the wave period can be one wavelength per block. As a result, the frequency of the undulation can be increased to further improve the quality of the printed image.

In the above-described invention, the light emitting element may be a light emitting diode such as an organic light emitting diode element or an inorganic light emitting diode element. Further, the light emitting device may be an optical head of an image forming apparatus or a display device in which a plurality of light emitting elements are arranged in a matrix.

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. First Embodiment>
FIG. 1 is a perspective view showing a partial configuration of an image forming apparatus using an optical head according to the first 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 includes the optical head 1 and the photosensitive drum 1.
10 is arranged. 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. An example of such a condensing lens array 15 is SLA (Selfoc Lens Array) available from Nippon Sheet Glass Co., Ltd. (Selfoc / SELFOC is a registered trademark of Nippon Sheet Glass Co., Ltd.). 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 arrangement of OLED elements used in the optical head 1 according to the first embodiment. As shown in the figure, the plurality of OLED elements are divided into n blocks B1 to Bn, and each of the blocks B1 to Bn includes four OLED elements. For example, the block B1 is composed of OLED elements P11, P12, P13, and P14. A plurality of OLED elements P11, P12,... Pn4 are linearly arranged in the main scanning direction X. Here, the main scanning direction X coincides with the direction of the print line, and the sub-scanning direction Y orthogonal thereto is the scanning direction with respect to the photoconductor 110. In the following description, when it is not necessary to specify each block and each OLED element, they are simply described as “B” and “P”.

FIG. 3 is a block diagram showing the configuration of the optical head 1. As shown in this figure, the optical head 1
The driving circuit 10, the control circuit 20, n demultiplexers 30-1 to 30-n, 4n light emitting circuits 40, and 4n OLED elements P11 to Pn4 are provided. Demultiplexer 30-1
˜30-n are provided corresponding to the blocks B1 to Bn, and the switches SW1 to SW4 are provided.
Is provided. The switches SW1 to SW4 are controlled so as to be exclusively turned on in a predetermined order according to the control signal CTL supplied from the control circuit 20.

The drive circuit 10 is supplied with an image signal Din that indicates the gradation of each of the OLED elements P11 to Pn4. In this example, the image signal Din designates gradation 0 to gradation 4. Then, the drive circuit 10 generates drive signals Q1, Q2,..., Qn obtained by time-division-multiplexing signals instructing on / off of the OLED elements P included in each block B.

For example, it is assumed that the image signal Din includes image data D11 to D24 corresponding to the OLED elements P11 to P24 as shown in FIG. Here, each image data is composed of 4 bits, and each bit designates turning on / off in one unit period of gradation control. In this example, as shown in FIG. 5, a period obtained by dividing one line period TA into four is one unit period of gradation control. Then, gradation 0 to gradation 5 are engraved by controlling turning on and off for each unit period T1 to T4.
For example, the bit b11-1 of the image data D11 designates lighting / extinguishing in the unit period T1, the bit b11-2 designates lighting / extinction in the unit period T2, and the bit b11-3 is lighting / extinction in the unit period T3. The turn-off is designated, and the bit b11-4 designates the turn-on / off in the unit period T4.

FIG. 6 shows a timing chart of the optical head 1. As shown in this figure, the drive signal Q1 is
Each bit of the image data D11 to D14 is rearranged. The drive signal Q2 is
Each bit of the image data D21 to D24 is rearranged. For example, the drive signal Q1 in the unit period T1 includes b11-1, b12-1, b13-1, and b14-1. And each switch SW1-SW4 of the demultiplexer 30-1 is each unit period T1-T.
4 is turned on in the order of SW1, SW2, SW3, SW4. As a result, the drive signal Q1 is distributed to the light emitting circuits 40 corresponding to the OLED elements P11 to P14. Each light emitting circuit 40 latches the drive signal Q1 in each unit period, and each OLED element P11.
Functions as a current source for supplying current to P14. In this example, the drive signals supplied to the OLED element 11 are b11-1, b11-2, b11-3, b11-4 as shown in the figure.

On the other hand, the drive signal Q2 in the unit period T1 is composed of b24-1, b23-1, b22-1 and b21-1. And each switch SW1-SW4 of the demultiplexer 30-2
Are turned on in the order of SW4 → SW3 → SW2 → SW1 in each of the unit periods T1 to T4. As a result, the driving signal Q2 corresponds to the light emitting circuit 40 corresponding to the OLED elements P21 to P24.
Distributed to. Each light emitting circuit 40 latches the output signal of the demultiplexer 30-1.

In this embodiment, in the adjacent blocks B1 and B2, OLED elements P11 and P11
24, OLED elements P12 and P23, OLED elements P13 and P22, OLE
A set of D elements P14 and P21 is sequentially selected. In other words, adjacent blocks B1 and B
2, the OLED elements P11 to P14 and P21 to P21 are arranged so that the light emission order is mirror-symmetric.
A drive signal is supplied by sequentially selecting P24.

FIG. 7 shows a latent image formed on the photoconductor 110. In this case, the OLED element P (P14) at the end of a certain block B (B1) and the OLE belonging to another block B (B2) adjacent thereto.
The latent images of the D element P (P21) coincide with each other in the sub-scanning direction Y, and there are no steps. The latent images formed by the OLED elements P belonging to the same block B are gradually shifted in the sub-scanning direction Y. As a result, since a large step does not occur in the latent image, it is possible to print a high-quality image while suppressing deterioration in resolution. Furthermore, since the OLED elements P are arranged linearly, the optical head 1 can be reduced in size in the main scanning direction.

<2. Second Embodiment>
FIG. 8 shows a block diagram of an optical head 2 according to the second embodiment, and FIG. 9 shows an arrangement of OLED elements P used in the optical head 2. The optical head 2 of the second embodiment includes eight OLED elements P in each block B, and each OLED element P is arranged on a straight line. Each demultiplexer 30-1 to 30-n performs a 1: 8 selection. In this example, unit periods T1-T4
Each of the eight switches SW1 to SW8 is exclusively turned on.

Here, assuming that the period synchronized with the switching of the switches SW1 to SW8 (the period obtained by dividing the unit period into eight) is t1 to t8, each switch S in the demultiplexers 30-1 and 30-2.
On / off of W1 to SW8 is as shown in FIG. Specifically, SW1 → S
W8.fwdarw.SW2.fwdarw.SW7.fwdarw.SW3.fwdarw.SW6.fwdarw.SW4.fwdarw.SW5. That is, each block B
Are sequentially selected from the outer end toward the center.

FIG. 11 shows a latent image formed on the photoconductor 110. In this case, the OLED element P (P18) at the end of a certain block B (B1) and the OL belonging to another block B (B2) adjacent thereto.
The latent images of the ED element P (P21) substantially coincide with each other in the sub-scanning direction, and the level difference between each OL in the block.
This is the same as the step of the ED element P. Further, the waviness W of the latent image is one wavelength per block. That is, in the second embodiment, there is one wave of the undulation of the latent image for every eight OLED elements. In the first embodiment, there are four OLED elements per block, and the total of two blocks is 8
There is one wave of undulation in the latent image per OLED element. In other words, OL per block
Even if the number of ED elements changes, the waviness wavelength of the latent image can be made the same, and the printing quality can be kept equal. The number of OLED elements per block is increased when, for example, the number of terminals is decreased and the number of driving ICs to be used is decreased in order to reduce the cost. In other words, for cost reduction, even if the number of OLED elements per block is increased, it is possible to obtain an effect that the print quality is not impaired.

Note that on / off of the switches SW1 to SW8 in the demultiplexers 30-1 and 30-2 may be controlled as shown in FIG. Specifically, SW5 → SW4 → S
W6 → SW3 → SW7 → SW2 → SW8 → SW1. That is, the OLED elements P included in each block B are sequentially selected from the center toward the outer end. The latent image in this case is obtained by reversing the peaks and valleys of the latent image shown in FIG.

<3. Third Embodiment>
The optical head 2 of the third embodiment is configured similarly to the optical head 2 of the second embodiment shown in FIG. 8 except for the arrangement of the OLED elements P.
FIG. 12 shows the arrangement of the OLED elements P of the third embodiment. In this example, the OLED elements P11 to P18 belonging to the block B1 are arranged on the print lines L1 to L8 displaced in the sub-scanning direction Y. Here, the distance E between the print lines is F for the width of one line and K for the number of gradations.
When the multiple of the demultiplexer is k, it is given by the following equation (1).
E = F / K / k (1)
The width F of one line is the width of a latent image formed on the photoconductor 110 when the OLED element P is on during one line period. F / K is the amount of movement of the photoconductor 110 during one gradation period.

In this example, the OLED elements P adjacent in the main scanning direction X are arranged in one print line. For example, a print line L2 exists between the OLED element P11 and the OLED element P12. That is, k (k is a natural number of 2 or more) OLs belonging to a certain block B
The ED element P is arranged on each of k print lines, and the k OLED elements P are m (m is 2).
The above natural numbers) are divided into groups, and in each group, O adjacent to the main scanning direction X.
The LED element P is arranged for every m print lines. In this example, k = 8, m = 2, and the OLED elements P11 to P14 form the first group G1, and the OLED elements P15 to P15
P18 forms the second group G2.

When the adjacent OLED elements P are arranged for every Z2 print lines in this manner, various wirings can be passed between the adjacent OLED elements P, and the degree of freedom in layout can be expanded.
Here, on / off of the switches SW1 to SW8 in the demultiplexers 30-1 and 30-2 is controlled as shown in FIG. Specifically, SW1 → SW5 → SW2 → SW6
→ SW3 → SW7 → SW4 → SW8. That is, a plurality of OLEDs belonging to block B
The element P is selected in the order of the sub-scanning direction Y. As a result, the latent image formed on the photoconductor 110 is shown in FIG.
As shown in FIG. 3, it becomes a straight line, and steps and undulations are eliminated.

<4. Fourth Embodiment>
The optical head 1 of the fourth embodiment is configured similarly to the optical head 1 of the first embodiment shown in FIG. 3 except for the arrangement of the OLED elements P.
FIG. 15 shows the arrangement of the OLED elements P of the fourth embodiment. OLED belonging to block B1
Elements P11 and P12 are arranged on the print line L1, and OLED elements P13 and P1.
4 is arranged on the print line L2. The same applies to the other blocks B2 to Bn. That is, although a plurality of OLED elements P are continuously arranged on the same print line, a gap can be formed between the OLED elements P at the places (P12 and P13) where the print lines are switched. Various wirings can be passed through this gap, and the degree of freedom in layout can be expanded.

Here, the distance E between the print lines is F continuously for the width of one line, K for the number of gradations, k for the multiple of the demultiplexer (the number of OLED elements belonging to one block), and continuously arranged on the same print line. When the number of OLED elements P is R, the following expression (2) is given.
E = F / k / K * R (2)

Further, on / off of the switches SW1 to SW4 in the demultiplexers 30-1 and 30-2 is controlled as shown in FIG. Specifically, SW1 → SW2 → SW3 → SW4. In this case, the latent image formed on the photoconductor 110 is as shown in FIG. 17 and is linear as shown in FIG.

<5. Fifth Embodiment>
The optical head 1 of the fifth embodiment is configured in the same manner as the optical head 1 of the first embodiment shown in FIG. 3 except for the arrangement of the OLED elements P.
FIG. 18 shows the arrangement of the OLED elements P of the fifth embodiment. In this example, the OLED elements P11 to P14 belonging to the block B1 are arranged on the print lines L1 to L4 displaced in the sub scanning direction Y. Here, the distance E between the print lines is F for the width of one line and K for the number of gradations.
When the multiple of the demultiplexer (the number of OLED elements belonging to one block) is k, it is given by the following equation (3).
E = F * (1-1 / K / k) (3)

Further, on / off of the switches SW1 to SW4 in the demultiplexers 30-1 and 30-2 is controlled as shown in FIG. Specifically, SW1 → SW2 → SW3 → SW4. The same applies to the other demultiplexers 30-1. OLE in block B1
The D elements P11 to P14 are arranged in the order of P14 → P13 → P12 → P11 with respect to the sub-scanning direction Y. On the other hand, the selection by the demultiplexer 30-1 is P11 → P12 → P1.
The order is 3 → P14. For this reason, as in the first embodiment, the order of the drive signals is changed to the switch SW.
If the order is 1 to SW4, the print results are shifted as shown in FIG. Therefore, the fifth
The driving circuit 10 according to the embodiment includes 1 to 2 OLED elements that are selected earlier.
The print data is post-fed and supplied line by line.

Specifically, print data is generated as shown in FIG. As a result, the latent image formed on the photoconductor 110 becomes a straight line as shown in FIG. 21, and steps and waviness are eliminated.
The distance E between the print lines may be given by the following equation (4). However, N is a natural number.
E = F * (N−1 / K / k) (4)

<6. Image forming apparatus>
As shown in FIG. 1, the optical head 1 or 2 according to each of the above embodiments 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. 22 is a longitudinal sectional view showing an example of an image forming apparatus using the optical head 1 or 2. 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, 1 having the same configuration are used.
M and 1Y are four photosensitive drums (image carriers) 110K, 110C, and 1 having the same configuration.
10M and 110Y are arranged at the exposure positions, respectively. Organic EL array exposure head 1K
, 1C, 1M, and 1Y are the optical heads 1 according to any one of the embodiments exemplified above.

As shown in FIG. 13, this image forming apparatus is provided with a driving roller 121 and a driven roller 122, and an endless intermediate transfer belt 120 is wound around these rollers 121 and 122, as indicated by arrows. 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, there are four photosensitive drums 1 each having a photosensitive layer on the outer peripheral surface.
10K, 110C, 110M, and 110Y are arranged at predetermined intervals. 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. Photosensitive drum 110K, 1
10C, 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), organic EL array exposure head 1 (K, C, M, Y), and developer 114 (K, C)
, M, Y) are arranged. 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. In each organic EL array exposure head 1 (K, C, M, Y), the arrangement direction of the plurality of OLED elements P is aligned with 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 with light by the plurality of light emitting elements 30 described above. The developing device 114 (K, C, M, Y) forms a visible image, ie, a visible image, on the photosensitive drum by attaching toner as a developer to the electrostatic latent image.

Black, cyan, magenta, and black formed by such a four-color monochromatic image forming station
The yellow visible images are sequentially transferred onto the intermediate transfer belt 120 to be superimposed on the intermediate transfer belt 120. As a result, a full-color visible image is obtained. Inside the intermediate transfer belt 120, four primary transfer corotrons (transfer units) 112 (K, C, M,
Y) is arranged. The primary transfer corotron 112 (K, C, M, Y) is disposed in the vicinity of the photosensitive drum 110 (K, C, M, Y), respectively, and the photosensitive drum 110 (K,
By electrostatically attracting the visible image from (C, M, Y), the visible image is transferred 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 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 by passing through a fixing roller pair 127 as a fixing unit. . Thereafter, the sheet 102 is discharged onto a paper discharge cassette formed on 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. 23 is a longitudinal sectional view of another image forming apparatus using the optical head 1 or 2. 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. 22, 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,
The plurality of light emitting elements 30 are arranged so that the arrangement direction thereof 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 includes four developing units 163Y, 163C, 163M, and 163K.
The drums are arranged at an angular interval of ° and can be rotated 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.
Further, the image is transferred to the intermediate 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, and an intermediate transfer is performed so as to overlap the yellow developed image. Transferred to the belt 169. In this way, while the photosensitive drum 165 rotates four times, yellow, cyan, magenta,
The black visible image is sequentially superimposed on the intermediate transfer belt 169, and as a result, a full-color visible image is formed on the transfer belt 169. 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 visible 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 next-color visible image.

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). And
The secondary transfer roller 171 moves the intermediate transfer belt 169 when transferring a full-color visible image 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.
75. 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. 22 and 23 uses the OLED element P as an exposure means, 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 illustrating a partial configuration of an image forming apparatus using an optical head according to the present invention. It is a top view which shows arrangement | positioning of the OLED element used for the optical head 1 which concerns on 1st Embodiment. 2 is a block diagram showing a configuration of an optical head 1. FIG. It is explanatory drawing which shows an example of the image signal Din. It is a timing chart which shows the relationship between a gradation and a line period. 3 is a timing chart showing the operation of the optical head 1. FIG. 3 is an explanatory diagram showing a latent image formed on a photoconductor by the same device. It is a block diagram which shows the structure of the optical head 2 which concerns on 2nd Embodiment. It is a top view which shows arrangement | positioning of the OLED element used for the apparatus. It is explanatory drawing which shows operation | movement of the demultiplexer used for the apparatus. FIG. 3 is an explanatory diagram showing a latent image formed on a photoconductor by the same device. It is a top view which shows arrangement | positioning of the OLED element used for the optical head of 3rd Embodiment. It is explanatory drawing which shows operation | movement of the demultiplexer used for the apparatus. FIG. 3 is an explanatory diagram showing a latent image formed on a photoconductor by the same device. It is a top view which shows arrangement | positioning of the OLED element used for the optical head of 4th Embodiment. It is explanatory drawing which shows operation | movement of the demultiplexer used for the apparatus. FIG. 3 is an explanatory diagram showing a latent image formed on a photoconductor by the same device. It is a top view which shows arrangement | positioning of the OLED element used for the optical head of 5th Embodiment. It is explanatory drawing which shows the printing result at the time of producing | generating a drive signal in the same order as 1st Embodiment. It is a timing chart which shows operation | movement of the apparatus. FIG. 3 is an explanatory diagram showing a latent image formed on a photoconductor by the same device. 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 structure of the other image forming apparatus using the optical head which concerns on this invention.

Explanation of symbols

1, 2... Optical head, P11 to Pn4... OLED element, SW1 to SW4.
10: Driving circuit, 30-1 to 30-n: Demultiplexer, 40: Light emitting circuit, Q1
Qn: drive signal, B1 to Bn: block.

Claims (7)

A plurality of light emitting elements arranged in a straight line;
Driving means for generating a drive signal obtained by time-division-multiplexing a signal for driving each light-emitting element belonging to the block for each of a plurality of blocks obtained by dividing the plurality of light-emitting elements;
Selecting means for selectively supplying the drive signal to each light emitting element belonging to the block;
The selection means selects the drive signal so that the light emission order of the light emitting elements is mirror-symmetric in adjacent blocks.
An optical head characterized by that. A plurality of light emitting elements arranged in a straight line;
Driving means for generating a drive signal obtained by time-division-multiplexing a signal for driving each light-emitting element belonging to the block for each of a plurality of blocks obtained by dividing the plurality of light-emitting elements;
Selecting means for selectively supplying the drive signal to each light emitting element belonging to the block;
In the selection means, the light emission order of the light emitting elements included in each block is from the center to the outer end,
Alternatively, the drive signal is selected so that the order is from the outer end to the center.
An optical head characterized by that. A plurality of light emitting elements are divided into a plurality of blocks, and k (k
Is a natural number of 2 or more) light emitting elements arranged on k lines parallel to the main scanning direction, and
a light emitting element group in which k light emitting elements are divided into m (m is a natural number of 2 or more) groups, and in each group, light emitting elements adjacent in the main scanning direction are arranged for each m lines;
Driving means for generating, for each of the plurality of blocks, a driving signal obtained by time-division-multiplexing a signal for driving each light emitting element belonging to the block;
Selection means for selectively supplying the drive signals to the k light emitting elements belonging to the block in order in the sub-scanning direction;
An optical head comprising: A plurality of light emitting elements are divided into a plurality of blocks, and k (k
Is a natural number of 2 or more) a light emitting element group in which light emitting elements are arranged on k lines parallel to the main scanning direction;
Driving means for generating, for each of the plurality of blocks, a driving signal obtained by time-division-multiplexing a signal for driving each light emitting element belonging to the block;
Selecting means for selectively supplying the drive signals to the k light emitting elements belonging to the block in order in the sub-scanning direction;
The distance E between the lines when F is the print width, K is the number of gradations, and N is a natural number,
E = F * (N−1 / K / k)
An optical head characterized in that An optical head according to any one of claims 1 to 4,
An image carrier on which an image is formed by light from the optical head;
An image forming apparatus comprising: In an optical head formed by linearly arranging a plurality of light emitting elements, the plurality of light emitting elements are divided into a plurality of blocks, and a control method for controlling the light emission order of the light emitting elements for each block,
Sequentially selecting the light emitting elements so that the light emission order is mirror-symmetric in adjacent blocks;
Supplying a driving signal to the light emitting elements sequentially selected,
A method for controlling an optical head provided. In an optical head formed by linearly arranging a plurality of light emitting elements, the plurality of light emitting elements are divided into a plurality of blocks, and a control method for controlling the light emission order of the light emitting elements for each block,
Sequentially selecting the light emitting elements included in each block from the center toward the outer end or the light emitting elements from the outer end toward the center;
Supplying a driving signal to the light emitting elements sequentially selected,
A method for controlling an optical head provided.

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