JP2009056795A - Image forming device, image forming method, and exposure head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure head which ensures improved image quality and to provide an image forming device and an image forming method which use the exposure head. <P>SOLUTION: The image forming device includes a photoconductor drum 150 having a rotational shaft in a first direction, and an exposure head 100 having a plurality of imaging optical systems 104 disposed in the first direction and a second direction perpendicular to the first direction and each having a negative optical magnification, and a light emitting element substrate 101 on which a plurality of light emitting elements 102 are disposed, the plurality of light emitting elements emitting light beams imaged on the photoconductor drum 150 by one of the imaging optical systems 104. The imaging optical systems 104 disposed in the second direction image the light beams on the photoconductor drum 150 and at positions different from each other in the second direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exposure head that suppresses deterioration in image quality, an image forming apparatus using the exposure head, and an image forming method.

  As an exposure light source for an image forming apparatus, a configuration in which a line head using LEDs is installed is known. Patent Document 1 proposes a technique for improving the resolution without reducing the arrangement pitch of the light emitters in the light emitter array. FIG. 17 is an explanatory diagram showing a schematic configuration of an image forming apparatus using the line head disclosed in Patent Document 1. 17A is a diagram viewed from the cross-sectional direction of the photoconductor 11, and FIG. 17B is a diagram viewed from obliquely above the photoconductor 11.

N rows (n = 2 in this example) of light emitter arrays 31 and 32 are arranged on the substrate 1, and monocular lenses 33 and 34 are provided in correspondence with the respective light emitter arrays 1: 1. The optical axes of the monocular lenses 33 and 34 are shifted from the center direction of the light beams from the light emitter arrays 31 and 32. With this configuration, the light from the n rows of light emitter arrays is imaged on the same line 35 of the photoconductor 11.
Japanese Patent No. 2868175

  In the example described in Patent Document 1, banding occurs when the driving system of the photosensitive member fluctuates (vibrates) around the set printing speed or cycle. For example, in the case of driving with a gear, a speed fluctuation occurs corresponding to the pitch of the gear, and banding appears in the image, and a striped image appears. For this reason, there has been a problem that image quality deteriorates. FIG. 18A shows an original image, and FIG. 18B shows an image formed on the image plane when banding is present.

  Further, when a line head mounted with a light emitting element is attached to the main body, the line head may be fixed at a position shifted from the reference position for attachment. This is called skew registration misalignment and causes image quality deterioration. FIG. 19A is an explanatory diagram of such skew registration deviation. An LED chip 35 on which a plurality of LED elements 36 are mounted is linearly arranged in the axial direction (main scanning direction) of the photoconductor to form a line head. The line head is inclined with respect to a reference position. Is fixed to the main body. C. L is the center line of the substrate. Skew resist misalignment also occurs when an organic EL element is used as the light emitting element.

  Further, when an LED is used as a light emitting element mounted on the line head, a curved resist shift occurs in which each LED chip is curvedly attached to the substrate. FIG. 19B is an explanatory diagram of such a curved registration shift. Center line of substrate C.I. With respect to L, each of the LED chips 35a to 35g is curved and mounted except for the LED chip 35b.

  When the LED chip is mounted on the line head, the skew resist deviation and the curved resist deviation occur in combination. FIG. 19C is an explanatory diagram of an example in which such skew registration deviation and curved registration deviation occur in combination. As described above, since the skew registration deviation and the curved registration deviation are combined, there is a problem in that the latent image position deviation (exposure position deviation) occurs in the photosensitive member and the image quality deteriorates.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to suppress the influence of banding and to improve the image quality by correcting the displacement of the latent image and the line head. It is an object of the present invention to provide an image forming apparatus and an image forming method used.

  SUMMARY An advantage of some aspects of the invention is that a plurality of image forming apparatuses according to the invention have a photosensitive drum having a rotation shaft in a first direction and a plurality of photosensitive drums in the first direction and the second direction. And an image forming optical system having a negative optical magnification, and a light emitting element substrate on which a plurality of light emitting elements for emitting light imaged on the photosensitive drum by the image forming optical system is disposed. And the light imaged by the imaging optical system arranged in the second direction forms an image at different positions in the second direction of the photosensitive drum. .

  In the image forming apparatus according to the present invention, the imaging optical system arranged in the second direction forms an image of light from the light emitting element at a position of the photosensitive drum different in the first direction. .

  In the image forming apparatus according to the present invention, the imaging optical system is arranged in a straight line in the first direction to form an imaging optical system row, and a plurality of the imaging optical system rows are provided. .

  The image forming apparatus according to the present invention includes a driving unit that drives the photosensitive drum, and a gear having a pitch G that transmits a driving force from the driving unit to the photosensitive drum. The width Da between the imaging optical system rows has a relationship of Da> (1/2) × G.

  In the image forming apparatus according to the present invention, the gear is disposed on a rotation shaft of the photosensitive drum.

  In the image forming apparatus according to the present invention, the photosensitive drum has a flange, and the gear is fixed to the flange.

  The image forming apparatus according to the present invention connects the driving unit and the photosensitive drum, and has a connection portion having a second rotation shaft, and the gear is disposed on the second rotation shaft. Is done.

  In the image forming apparatus according to the present invention, the light-emission timing of the light-emitting elements is varied in the imaging optical system row to form a linear or substantially linear latent image in the first direction of the photosensitive drum. Have means.

  In the image forming apparatus according to the present invention, the imaging optical system includes two or more lenses.

  In the image forming apparatus according to the present invention, the light emitting element is an organic EL light emitting element.

  The image forming method according to the present invention includes a first imaging optical system row in which a plurality of imaging optical systems having a negative optical magnification in the first direction are arranged, and a negative optical magnification in the first direction. A plurality of imaging optical systems having a first imaging optical system row, a second imaging optical system row that forms an image at a position of the photosensitive drum that is different from the first imaging optical system row in a second direction, and Light that has a plurality of light emitting elements that emit light that is imaged by the imaging optical system and a photosensitive drum that moves in the second direction, and that is imaged in the first imaging optical system row To form a latent image on the photosensitive drum, to form a latent image in the first imaging optical system row, and then to move the photosensitive drum for a predetermined time; After the movement, the light imaged by the second imaging optical system row is emitted to form a latent image on the photosensitive drum. And having a degree, the.

An exposure head according to the present invention includes a first imaging optical system row in which a plurality of imaging optical systems having a negative optical magnification in the first direction are arranged, and a negative optical magnification in the first direction. A plurality of imaging optical systems, and a second imaging optical system row that forms an image at a different position in the second direction from the first imaging optical system row, and the one imaging optical system. And a plurality of light-emitting elements that emit light to be imaged.

  In the exposure head according to the present invention, a plurality of the plurality of light emitting elements that emit light imaged by the one imaging optical system are arranged in a first direction and a second direction.

  According to the image forming apparatus, the image forming method, and the exposure head of the present invention as described above, the shading due to banding is scattered all over the formed image, so that it is possible to suppress image quality deterioration due to banding. Become.

  In connection with the present invention, it is confirmed that the following reference embodiments are also effective configurations. That is, a line head according to a reference embodiment of the present invention includes a substrate and a light emitting body in which a plurality of light emitting elements are arranged on the substrate along the axial direction (main scanning direction) of the photosensitive body to form a light emitting element group row. And an imaging lens array provided corresponding to the light emitter array, and the light emitter array and the imaging lens array are arranged in a plurality of rows with respect to the moving direction (sub-scanning direction) of the photosensitive member. The latent image is formed at a different position for each row with respect to the photoconductor.

  In the line head according to the reference embodiment of the present invention, the row pitch of the latent image is formed to be longer than ½ of the gear pitch of the driving unit of the photosensitive member.

  The line head of the present invention is characterized in that a plurality of light emitting element group rows are formed in the light emitter array in the moving direction of the photoconductor.

  In the line head according to the reference embodiment of the present invention, the light emitting elements of the light emitter array are divided into light emitting element groups corresponding to the individual imaging lenses of the imaging lens array. To do.

  Moreover, the line head according to the reference embodiment of the present invention is characterized in that the light emitting element is formed of an organic EL light emitting element.

  In an image forming apparatus according to a reference embodiment of the present invention, an image forming unit including a charging unit, any of the line heads described above, a developing unit, and a transfer unit is arranged around an image carrier. At least two or more forming stations are provided, and a transfer medium passes through each of the image forming stations, thereby performing image formation by a tandem method.

  In addition, the image forming apparatus according to the reference embodiment of the present invention includes a control unit for the line head, and the control unit controls the light emitting operation of the light emitting elements for each of the light emitting element group rows to control the latent image. It is characterized by preventing the occurrence of image displacement.

  Further, in the image forming apparatus according to the reference embodiment of the present invention, the control for varying the light emitting operation of the light emitting element for each light emitting element group row is performed by using time delay data relative to the reference operation or absolute time. The control is based on timing data, and is characterized by comprising storage means for storing the delay data or timing data.

  The image forming apparatus according to the reference embodiment of the present invention is characterized in that the control means is provided in an external controller.

  The image forming apparatus according to the reference embodiment of the present invention is characterized in that the control unit is provided in the line head.

  In the image forming method according to the reference embodiment of the present invention, at least two or more image forming stations for forming a latent image by the line head described above are provided on the photoconductor to form an image by a tandem method. A step of acquiring correction data for correcting a displacement of the latent image forming position, a step of storing the correction data in a storage unit, and a step of reading the correction data from the storage unit and providing the correction data to the line head. And a step of controlling the light emitting operation of the light emitting elements differently for each light emitting element group row.

The present invention will be described below with reference to the drawings. FIG. 2 is an explanatory view showing an embodiment of the present invention. FIG. 2A is a view of the photosensitive member 11 as viewed in the axial direction, and FIG. 2B is a view of the photosensitive member 11 and the line head 10 as viewed obliquely from above.
The line head 10 includes a light emitter array 38 and 39 in which a plurality of light emitting elements are provided on the substrate 1 along the axial direction (main scanning direction) of the photoreceptor 11 with respect to the movement direction (Y direction) of the photoreceptor. Two rows are arranged.

  Reference numerals 4 and 5 denote imaging lens arrays formed of a microlens array (MLA) using microlenses having a negative optical magnification. The output light of the light emitting element passes through the imaging lens arrays 4 and 5, and latent images are formed on the photoconductor 11 at different positions 12 and 13. As the imaging lens arrays 4 and 5, an SLA (selfoc lens array) may be used.

  FIG. 1 is an explanatory diagram showing the positional relationship between the light emitter arrays 38 and 39 and the imaging lens arrays 4 and 5 of FIG. In FIG. 1, a light emitting element group row 7 is formed on a substrate 1 by arranging a plurality of light emitting elements 2 along the axial direction of a photoconductor (latent image carrier) 11. The light emitting element group row 7 corresponds to the light emitter arrays 38 and 39. In the example of FIG. 1, the light emitter arrays 38 and 39 are arranged in two rows with respect to the moving direction (Y direction) of the photosensitive member. The moving direction of the photoconductor can be regarded as a direction (sub-scanning direction) orthogonal to the axial direction of the photoconductor. Corresponding to the light emitter arrays 38 and 39, imaging lens arrays 4 and 5 are arranged. That is, the imaging lens arrays 4 and 5 are arranged in a plurality of rows in the moving direction of the photosensitive member.

  The individual image forming lenses 4a and 5a of the image forming lens arrays 4 and 5 correspond to the light emitting element groups 6 obtained by grouping a plurality of light emitting elements 2 into sections. Further, for example, the light emitter array 39 corresponds to the imaging lens array 5 as the light emitter group row 7. That is, in the embodiment of the present invention, a plurality of rows of imaging lens arrays are arranged in the moving direction of the photosensitive member, and a light emitting element group is associated with each imaging lens. In addition, one row of imaging lens arrays arranged in the axial direction of the photosensitive member corresponds to one row of light emitter groups. In the example of FIGS. 1 and 2, an organic EL element is used as the light emitting element 2.

  FIG. 3 is an explanatory diagram showing an embodiment of the present invention. In FIG. 3, the line head 10 arranges the light emitter arrays 38 to 40 on the substrate 1 in a line shape in the axial direction of the photoconductor 11. Reference numerals 4a, 5a, and 14a denote imaging lenses. In the characteristic diagram, the vertical axis H indicates the speed unevenness caused by banding of the driving device that drives the photoconductor 11, and the horizontal axis L indicates the distance in the direction orthogonal to the axial direction of the photoconductor 11. The speed unevenness characteristic T at this time fluctuates periodically with the gear pitch G of the driving device for driving the photoconductor 11 as one period.

In the embodiment of the present invention, as described with reference to FIG. 2, the imaging position in the photosensitive member rotation direction is different for each row of the lens array. Therefore, the latent image row in the axial direction (main scanning direction) formed on the photoconductor 11 meanders. The pitch Da between the imaging lenses 4a and 5a (pitch in the sub-scanning direction) Da corresponds to the row pitch of the latent image formed on the photoconductor. If this pitch Da is formed to be longer than ½ of the gear pitch G of the drive device, the peaks and valleys of the speed variation characteristic T cancel each other, making it difficult to understand the influence of banding.

  FIG. 4 is an explanatory diagram showing an example of a latent image row formed on the photosensitive member. 4A is an original image, FIG. 4B is a conventional latent image row, and FIGS. 4C to 4E are latent image rows according to the embodiment of the present invention. This is an example in which the pitch Da in the sub-scanning direction is changed. As described above, in the embodiment of the present invention, since the latent image row in the main scanning direction meanders, deterioration in image quality due to banding can be suppressed more than the conventional latent image row. Note that the pitch in the sub-scanning direction between the imaging lenses (the row pitch of the latent image row) is set to (c) <(d) <(e).

  FIG. 5 is a flowchart of an example of acquiring the positional deviation data of the line head described in the example of FIG. 19, and FIG. 6 is an explanatory diagram thereof. In FIG. 5, when the line head is manufactured, the bending deviation amount of the LED chip is measured (S20). In FIG. 6A, the center line C.V. The bending deviation amount E of each LED chip 35a to 35g from L is measured.

  Next, the line head is attached to the image forming apparatus in FIG. 5, and the amount of bending deviation of each LED chip is stored in the memory in advance when the image forming apparatus is shipped (S21). In this process, in FIG. 6B, the bending deviation amount E of each LED chip is stored in the memory 37 in advance. As the memory 37, an EEPROM (nonvolatile memory) can be used as will be described later. Subsequently, in FIG. 5C, the deviation amount of the LED chip is read at the time of printing. This deviation amount is obtained by adding the skew deviation amount to the curvature deviation amount (S23). This process corresponds to the process of FIG. In the example of FIGS. 5 and 6, an example in which an LED is used as the light emitting element is described. However, the same processing is performed even when an organic EL element is used as the light emitting element.

  FIG. 6D is an explanatory diagram of an example in which the print start timing of each LED chip is adjusted according to the LED chip shift amount F. FIG. Adjustment of the printing start timing of the light emitting element will be described with reference to FIG. FIG. 7A shows original image data, that is, image data Pa created by an external controller or the like so as to be printed. The LED chips 35a to 35g are arranged on the line head at positions shifted from the LED chip 35c at the reference position as shown in FIG. FIG. 7B schematically shows a memory for driving each LED chip. For example, the LED chips 35a are arranged so as to be shifted by two lines in the Y direction of the rotation direction of the photosensitive member as viewed from the LED chip 35c at the reference position. Therefore, the LED chip 35a is driven at a timing delayed by two lines from the LED chip 35c at the reference position by the memory 37a stacked in two stages.

  As described above, the use of the memory 37 adjusts the print start timing corresponding to the amount of deviation in the sub-scanning direction with respect to the reference position of each LED chip, thereby suppressing image quality deterioration caused by the position deviation of the LED chip. Can do. FIG. 7D shows a latent image Pb formed on the photoconductor. As shown in FIG. 7D, the same image data Pb as the original image data Pa is formed on the photoreceptor.

  FIG. 8 is a block diagram of the control unit in the embodiment of the present invention. The line head 10 is provided with a driver IC 24 that controls the light emitting elements, and an EEPROM 25 that stores delay information formed based on the curve deviation of the line head. The control unit 20 is provided with a print controller 21, a mechanical controller 22, and a head controller 23.

The print controller 21 has an image processing unit 21a, and the mechanical controller 22 has an arithmetic processing unit (CPU) 22a. The head controller 23 has an EE.
PROM communication control unit 23a, UART (Universal Asynchronous)
(Receiver Transmitter) control unit 23b, Video I / F 26,
A sub-scanning deviation correction unit 27 having a memory 27a, a head control signal generation unit 28, and a request signal generation unit 29 are provided. Information detected by the registration sensor 30 is input to the mechanical controller 22.

  Next, the control procedure of FIG. 8 will be described. For conversion reasons, the circled numbers are written as ◯ 1. When the printer is turned on, the EEPROM communication control unit 23a reads the delay information from the EEPROM 25 and transmits it to the UART communication control unit 23b (◯ 1). The method for acquiring the delay information will be described later with reference to FIG. The UART communication control unit 23b transmits delay information to the mechanical controller 22 (（2).

  The mechanical controller 22 prints a resist pattern, detects the printing result by the resist sensor 30, and calculates skew information (○ 3). The mechanical controller 22 adds the delay information to the skew information to calculate the sub-scanning deviation information, and transmits it to the UART communication control unit 23b (◯ 4). The UART communication control unit 23b transmits the sub-scanning deviation information to the sub-scanning deviation correcting unit 27 (◯ 5). The sub-scanning deviation correction unit 27 stores the received sub-scanning deviation information in the register of the memory 27a.

When printing is started, the mechanical controller 22 detects the paper edge and transmits a Vsync signal (video synchronization signal) to the request signal generation unit 29 (（6). The request signal generation unit 29 generates a Vreq signal (video data request signal) and an Hreq signal (line data request signal) and transmits them to the Video I / F unit (○ 7). At the same time, the Hreq signal is also transmitted to the sub-scanning deviation correction unit 27 and the head control signal generation unit 28 to synchronize the modules. The Video I / F unit 26 transmits the Vreq signal and the Hreq signal to the print controller (○ 8).

  The print controller 21 transmits the image processed image data to the Video I / F unit 26 using the received Vreq signal and Hreq signal as a trigger (（9). At this time, in order to reduce wiring costs and facilitate wiring, it is desirable to convert parallel image data into serial data (para-to-serial conversion) and transmit by high-speed serial communication. The video I / F unit 26 converts the image data from serial to parallel and transmits the image data to the sub-scanning deviation correction unit 27 (◯ 10).

  The sub-scanning deviation correction unit 27 corrects the sub-scanning deviation of the latent image forming position with a predetermined main scanning resolution using a plurality of line memories, and transmits the corrected image data to the line head 10 (◯ 11). At the same time, the head control signal generator 28 generates various head control signals (clock, start signal, reset signal, etc.) and transmits them to the line head 10 (◯ 11). Here, it is desirable to set the main scanning resolution of the sub-scanning deviation correction to LED chip units (consisting of a predetermined number of light emitting elements that can be controlled by one drive circuit) or lens units (light emitting element group units). This makes it possible to correct a sub-scanning deviation that occurs at the joint of the LED chip or the joint of the lens.

  FIG. 9 is a flowchart showing a procedure for acquiring delay information stored in the EEPROM 25 of FIG. In FIG. 9, the curve information of the line head is acquired first (◯ 1). In this process, the bending amount of the line head is measured by an optical sensor or the like (S1), and the bending information converted into line units is obtained (S2). Next, the number of correction lines is calculated (○ 2). In this process, the lens row pitch (S3), the photoreceptor surface speed (S4), and the transfer time (S5) of one line data are obtained. The number of MLA correction lines is calculated using these numerical values and equations (1) and (2) described later (S6). In the next process (○ 3), the delay information is calculated by adding the curvature information and the number of MLA correction lines (S7).

  Thereafter, the following processing is performed. Delay information is stored in the EEPROM (（4, S8). An image with a straight line drawn in the main scanning direction is printed (（5, S9). The amount of exposure timing deviation between the lenses of the printing result is measured with an optical microscope or the like (◯ 6, S10). Subsequently, the amount of exposure delay between lenses, curvature information, and the number of MLA correction lines are added (S11), and delay information is calculated again (○ 7, S12). Finally, delay information is stored in an EEPROM (nonvolatile memory) (（8, S13).

FIG. 10 is an explanatory diagram of an example of calculating the number of MLA correction lines. In the coupling lens arrays 38 to 40, single coupling lenses 4, 5, and 14 are arranged. In the coupled lens array 38, light emitting element group rows 7 are arranged correspondingly. Reference numeral 6 denotes a light emitting element group. Light emitting element group rows are also arranged corresponding to the other coupling lens arrays 39 and 40. When correcting the exposure position deviation of each light emitting element row of the MLA in line units (sub-scanning direction resolution), the correction line number Nhn is expressed by the following equation (1) from the coupled lens row pitches Da and Db and the photoreceptor surface speed Vopc. , (2).

The exposure delay time Tdly of the light emitting element row is the inter-lens pitch Da,
Tdly = Da / Vopc (1)
It becomes. If the transfer time of one line data is Thr, the number of MLA correction lines Nhn is
Nhn = Tdly / Thr (2)
It becomes. Actually, the number of lines Nhn is obtained by rounding off the decimal point.

FIG. 11 is a block diagram of the control unit 20a according to another embodiment of the present invention. The same parts as those in FIG. 8 are denoted by the same reference numerals, and detailed description thereof is omitted. The line head is provided with a sub-scanning deviation correction unit 27 in addition to the driver IC 24 and the EEPROM 25. The sub-scanning deviation correction unit 27 has a function as a delay circuit as will be described later. The configurations of the print controller 21 and the mechanical controller 22 are the same as those in FIG. The head controller 23 includes a video I / F 26, a head control signal generator 28, and a request signal generator 29.
Is provided.

Next, the processing procedure of FIG. 11 will be described. When the power of the printer is turned on, the previously stored sub-scanning deviation information is read from the EEPROM and transmitted to the sub-scanning deviation correction unit (delay circuit) (◯ 1). Acquisition of the sub-scanning deviation information will be described with reference to FIG. When printing is started, the mechanical controller 22 detects the edge of the paper and transmits a Vsync signal to the request signal generator (（2). The request signal generator 29 generates a Vreq signal (video data request signal) and an Hreq signal (line data request signal) to generate a video I / F unit 26.
(○ 3). At the same time, the Hreq signal is also transmitted to the sub-scanning deviation correction unit 27 and the head control signal generation unit 28 to synchronize the modules.

  The Video I / F unit 26 transmits the Vreq signal and the Hreq signal to the print controller 21 (◯ 4). The print controller 21 transmits the image processed image data to the Video I / F unit 26 using the received Vreq signal and Hreq signal as a trigger (◯ 5). At this time, it is desirable to convert parallel image data into serial data (serial-to-parallel conversion) and transmit by high-speed serial communication in order to reduce wiring costs and facilitate wiring.

The Video I / F unit 26 converts the image data from serial to parallel and transmits the image data to the sub-scanning deviation correction unit 27 of the head (（6). The sub-scanning deviation correction unit 27 corrects the sub-scanning deviation with a predetermined main scanning resolution using a plurality of line memories, and transmits it to the driver IC of the line head (（7). At the same time, the head control signal generator 28 generates various head control signals (clock, start signal, reset signal, etc.) and transmits them to the line head driver IC (（7).

FIG. 12 is a flowchart showing a procedure for acquiring latent image formation position shift information in the sub-scanning direction. 12, the same step (S) number is attached | subjected about the same process as FIG. Moreover, since the processing content of (circle) 1-(circle) 6 is the same as FIG. 9, description of the number of the round mark of this part is abbreviate | omitted.
The amount of curve of the line head is measured with an optical sensor or the like (S1), and the curve information converted into line units is obtained (S2). Further, the number of MLA correction lines is calculated using the lens row pitch (S3), the photoreceptor surface speed (S4), the transfer time of one line data (S5), and the equations (1) and (2) (S6). .

  Next, delay information is calculated by adding the curvature information (S2) and the number of MLA correction lines (S6) (S7), and the delay information is stored in the EEPROM (S8). Subsequently, an image with a straight line drawn in the main scanning direction is printed (S9), and the amount of exposure timing deviation between the lens rows in the printing result is measured with an optical microscope or the like (S10). Also, the resist pattern is printed (○ 7, S14), the printing result is detected by a resist sensor or the like, and skew information is calculated (○ 8, S15).

  In the process of S17, the sub-scanning deviation information is calculated by adding the lens row exposure timing deviation amount (S10), the skew information (S15), the curvature information (S2), and the number of MLA correction lines (S16) (○ 9). , S18). The sub-scanning deviation information is stored in the EEPROM (O10, S19).

  FIG. 13 is an explanatory diagram showing a latent image when the MLA exposure position shift is not corrected. In FIG. 13, Ta indicates an MLA inter-lens exposure position shift, and Tb indicates an MLA intra-lens exposure position shift. Reference numerals 6a, 6b and 6c denote patterns of latent images formed on the photosensitive member by output light transmitted through the imaging lens arrays 38, 39 and 40 described with reference to FIG.

  FIG. 14 is an explanatory diagram showing a latent image when the exposure position deviation of the MLA is corrected. . At this time, the latent image 15 is formed on the photosensitive member like 17a to 17f by the output light transmitted through each ML. That is, the latent image is formed linearly in the axial direction (main scanning direction) of the photoreceptor. For this reason, deterioration of image quality can be suppressed. In this correction, if the moving direction of the photosensitive member is Y, the following processing is performed. In the example of the latent image pattern 6a in FIG. 13, the in-lens exposure position deviation correction is performed with the latent image row k as a reference. That is, the latent image sequence m is formed at a timing delayed by one row from the latent image sequence k. Further, the latent image row n is formed at a timing delayed by two rows from the latent image row k.

  Similarly, the latent image patterns 6b and 6c are also subjected to exposure position shift correction by delaying the latent image row by row. In the lens row exposure position correction, the latent image pattern 6b is delayed by one timing in the Y direction with reference to the latent image pattern 6a, and the latent image pattern 6c is delayed by two timings in the Y direction. Therefore, the actual exposure position deviation correction is formed by delaying the timing in the Y direction sequentially for each line image row m to u with reference to the latent image row k of the latent image pattern 6a. Such delay control can be performed in a configuration in which memories are overlapped as described in the schematic diagram of FIG.

FIG. 15 is an explanatory diagram showing another example of latent image formation. Since there are individual differences in the pitch between the MLA lens rows and the diameter of the photoconductor, an error occurs in the lens row pitch Da and the photoconductor surface speed Vopc. That is, the number of MLA correction lines Nhn differs depending on the individual difference between the MLA and the photoconductor. Therefore, since the ideal inter-lens pitch and the number of MLA correction lines obtained from the ideal photoreceptor surface speed are different, when a linear latent image is drawn in the main scanning direction with an actual image forming apparatus, the MLA and the photoreceptor Due to individual differences, a slight step (inter-lens exposure timing shift) occurs at the lens boundary. FIG. 15 shows a latent image in which a slight step is generated at the lens boundary due to the individual difference between the MLA and the photosensitive member when the exposure position deviation of the MLA is corrected.

  In the embodiment of the present invention, a tandem color printer that exposes four photoconductors with four line heads, simultaneously forms four color images, and transfers them onto one endless intermediate transfer belt (intermediate transfer medium). The target is a line head used in (image forming apparatus). FIG. 16 is a vertical side view showing an example of a tandem image forming apparatus using an organic EL element as a light emitting element. In this image forming apparatus, four line heads 101K, 101C, 101M, and 101Y having the same configuration are exposed to four corresponding photosensitive members (image carriers) 41K, 41C, 41M, and 41Y having the same configuration. They are arranged at each position.

  As shown in FIG. 16, this image forming apparatus is provided with a driving roller 51, a driven roller 52, and a tension roller 53, and is an intermediate transfer belt that is circulated and driven in the direction indicated by the arrow (counterclockwise) by the tension roller 53. (Intermediate transfer medium) 50 is provided. Photosensitive members 41K, 41C, 41M, and 41Y are arranged at predetermined intervals with respect to the intermediate transfer belt 50. K, C, M, and Y added after the reference sign mean black, cyan, magenta, and yellow, respectively. The photoconductors 41 </ b> K to 41 </ b> Y are driven to rotate in the direction indicated by the arrow (clockwise) in synchronization with the driving of the intermediate transfer belt 50. Around each photoconductor 41 (K, C, M, Y), charging means 42 (K, C, M, Y) and a line head 101 (K, C, M, Y) are provided.

  Further, a developing device 44 (K, C, M, Y) that applies a toner as a developer to the electrostatic latent image formed by the line head 101 (K, C, M, Y) to form a visible image; The primary transfer roller 45 (K, C, M, Y) and the cleaning device 46 (K, C, M, Y) are included. The emission energy peak wavelength of each line head 101 (K, C, M, Y) and the sensitivity peak wavelength of the photoconductor 41 (K, C, M, Y) are set to substantially coincide.

  The black, cyan, magenta, and yellow toner images formed by the four-color single-color toner image forming station are intermediated by the primary transfer bias applied to the primary transfer roller 45 (K, C, M, Y). The toner image, which is sequentially primary transferred onto the transfer belt 50 and sequentially superposed on the intermediate transfer belt 50 to become a full color, is secondarily transferred to a recording medium P such as paper by a secondary transfer roller 66, and serves as a fixing unit. The toner is fixed on the recording medium P by passing through the fixing roller pair 61, and is discharged onto a paper discharge tray 68 formed in the upper part of the apparatus by a paper discharge roller pair 62.

  63 is a paper feed cassette in which a large number of recording media P are stacked and held, 64 is a pickup roller for feeding the recording media P from the paper feed cassette 63 one by one, and 65 is a secondary transfer portion of the secondary transfer roller 66. A pair of gate rollers for defining the supply timing of the recording medium P to the roller, 66 is a secondary transfer roller as a secondary transfer means for forming a secondary transfer portion with the intermediate transfer belt 50, and 67 is an intermediate after the secondary transfer. This is a cleaning blade that removes toner remaining on the surface of the transfer belt 50.

  In the embodiment of the present invention, an LED, an organic EL, a VCSEL (Vertical Cavity Surface Emitting Laser (Vertical Cavity Surface Emitting Laser)), or the like can be used as a light emitting element of the light emitter array. Moreover, as a lens array, SLA (Selfoc Lens Array), MLA (Micro Lens Array), etc. can be used.

Next, another embodiment of the present invention will be described. FIG. 20 is a diagram illustrating a portion centered on the exposure head and the photosensitive drum of an image forming apparatus according to another embodiment. FIG. 20A is a diagram illustrating the rotational axis of the photosensitive drum from the first direction. It is the figure which looked at the said site | part, and FIG.20 (B) is the figure which looked at the said site | part from the direction orthogonal to a 1st direction. FIG. 21 is a view showing the arrangement relationship between a light emitting element and an imaging optical system in an exposure head of an image forming apparatus according to another embodiment.

  20 and 21, 100 is an exposure head, 101 is a light emitting element substrate, 102 is a light emitting element, 103 is a light emitting element group, 104 is an imaging optical system, 105 is a light emitting element row, 106 is an imaging optical system row, Reference numeral 110 denotes an imaging lens, 150 denotes a photosensitive drum, 155 denotes a rotation shaft, and 160 denotes a gear. The exposure head 100 corresponds to the line head described in the previous embodiment.

  The exposure head 100 has an elongated shape along the rotation axis 155 of the photosensitive drum 150 and is disposed so as to face the photosensitive drum 150. Here, in this specification, the direction of the rotating shaft 155 of the photosensitive drum 150 is defined as the first direction. The rotating shaft 155 of the photosensitive drum 150 is provided with a gear 160, and the photosensitive drum 150 rotates by obtaining a rotational driving force from a driving device (not shown) via the gear 160. The surface of the photosensitive drum 150 is charged by a charging unit (not shown), and the exposure head 100 writes an electrostatic latent image on the surface.

  As a light source of the exposure head 100, a plurality of light emitting elements 102 are provided on the light emitting element substrate 101, and the light emitting elements 102 emit light selectively. Then, the light from the light emitting element 102 is condensed on the surface of the photosensitive drum 150 by the imaging optical system 104, whereby a predetermined electrostatic latent image is written on the surface of the photosensitive drum 150.

  In the present embodiment, an organic EL element is used as the light emitting element 102 provided on the light emitting element substrate 101. When such an organic EL element is used, it is relatively easy to manufacture a plurality of light emitting elements 102 on one light emitting element substrate 101, and an exposure head is not manufactured using a plurality of light emitting element substrates. There is an advantage that adjustment and the like are easier than in the case of an LED element that should not be. However, in the present invention, it is of course possible to use an LED element as the light emitting element 102.

  In the present embodiment, a single imaging lens 110 is used as the imaging optical system 104, but a plurality of imaging lenses are used as the imaging optical system 104, so that the optical It is also possible to improve the accuracy.

  In the present embodiment, a lens array is used in which a plurality of imaging lenses 110 are arranged two-dimensionally to form one component.

  In the present embodiment, the imaging optical system 104 uses an array of microlenses and is an imaging optical system having a negative optical magnification. Instead of the micro lens array (MLA) that is an imaging optical system having such a negative optical magnification, an SLA (selfoc lens array) that is an imaging optical system having a positive optical magnification may be used. good.

  As shown in FIG. 21, seven light emitting elements 102 of the light emitting element substrate 101 form one light emitting element group 103, and light collection of all the light emitting elements 102 belonging to this one light emitting element group 103 is performed. A single imaging optical system 104 is responsible for this.

A plurality of light emitting element groups 103 are arranged along the first direction to form a light emitting element row 105. An imaging optical system row 106 is formed so as to correspond to the light emitting element group 103 along the first direction. Here, in this specification, the direction in which the surface of the photosensitive drum 150 moves in the direction orthogonal to the first direction is defined as the second direction.

  On the light emitting element substrate 101, three light emitting element rows 105 are provided in the second direction so as to be slightly shifted in the first direction. Corresponding to this, as shown in the figure, the imaging optical system rows 106 are also provided so as to be slightly shifted in the first direction by three rows. Because of this arrangement relationship, the light imaged by the imaging optical system rows respectively arranged in the second direction is imaged at different positions in the second direction of the photosensitive drum 150, and The image is formed at different positions in the first direction. According to such an arrangement relationship, image quality deterioration due to banding can be made inconspicuous.

  According to the configuration as described above, the shading due to banding is scattered in the formed image, so that it is possible to suppress deterioration in image quality due to banding.

  Further, in the exposure head 100, since the light emitting element rows 105 are arranged as described above, in order to form a linear or substantially linear latent image in the first direction of the photosensitive drum 150, The light emission timings of the light emitting elements are different for each imaging optical system row, such as light emission of the first light emitting element row 105 → light emission of the second light emitting element row 105 → light emission of the third light emitting element row 105. Control is performed.

  FIG. 22 is a diagram schematically showing the exposure head 100 and the photosensitive drum 150. As shown in FIG. 22, the exposure head 100 includes a light emitting element substrate 101 and light emitting element rows 105 arranged in a line in the axial direction (first direction) of the photosensitive drum 150. The imaging lens 110 is an imaging lens and constitutes the imaging optical system 104.

  In the characteristic diagram shown in FIG. 22, the vertical axis H represents speed unevenness caused by banding of the driving mechanism that drives the photosensitive drum 150, and the horizontal axis L represents the distance in a direction orthogonal to the axial direction of the photosensitive drum 150. ing. The speed unevenness characteristic T at this time fluctuates periodically with the gear pitch G of the drive mechanism for driving the photosensitive drum 150 as one period.

  In the embodiment of the present invention, the imaging position in the rotation direction of the photosensitive drum is different for each imaging optical system row 106. Therefore, if all the light emitting elements of the exposure head 100 emit light once at the same time, the latent image in the axial direction (main scanning direction) formed on the photosensitive drum 150 is the same as the arrangement of the light emitting elements in FIG. Will meander.

  The pitch Da between the imaging lenses 110 (pitch in the sub-scanning direction) Da corresponds to the row pitch of the latent image formed on the photosensitive drum 150. If this pitch Da is formed to be longer than ½ of the gear pitch G of the drive mechanism, the peaks and valleys of the speed unevenness characteristic T cancel each other, making it difficult to understand the influence of banding.

  Note that the gear pitch G in this embodiment is not the pitch of the gear 160 itself. The gear pitch G in the present embodiment is obtained by converting the gear pitch of the gear 160 itself into a pitch on the surface of the photosensitive drum 150.

FIG. 23 is a diagram illustrating a method for calculating the gear pitch G in the embodiment of the present invention.
23, Pg represents the actual gear pitch of the gear 160, Dg represents the pitch circle diameter of the gear 160, and Dpc represents the diameter of the photosensitive drum 150. At this time, the gear pitch G in this embodiment is calculated by G = Pg × (Dpc / Dg).

In summary, in the present embodiment, it is assumed that a gear 160 having a pitch G for transmission to the photosensitive drum 150 is provided and the width between the imaging optical system rows 106 is Da.
Da> (1/2) × G
By configuring so that the relationship exists, it is possible to obscure the influence of banding.

  FIG. 24 is a diagram showing the effect of the present invention. FIG. 24A is a diagram showing an image in which banding has not occurred at all, and FIG. 24B is a diagram showing an image in the case where banding has occurred in a conventional image forming apparatus, and FIG. FIG. 4 is a diagram showing an image when banding occurs in the image forming apparatus of the present invention.

  FIG. 24B shows an image formed by an exposure head in which a conventional light emitting element is provided only along one row in the first direction. On the other hand, FIG. 24C shows an image formed by the exposure head of the present invention. In each of FIGS. 24A and 24B, as a numerical example, an image when the pitch G = 1.2 mm and the pitch Da = 0.8 mm is shown.

  In the image of FIG. 24B, since shading due to banding occurs periodically in the vertical direction, image deterioration due to banding becomes very noticeable. On the other hand, in the image of FIG. 24C, the occurrence of shading due to banding is scattered all over the image, so image quality deterioration due to banding is not noticeable.

  Next, another embodiment of the present invention will be described. FIG. 25 is a view showing a part extracted from the center of the exposure head and the photosensitive drum of an image forming apparatus according to another embodiment, and is a view of the part from a direction orthogonal to the first direction. In the present embodiment, the photosensitive drum 150 is provided with flanges 151 at both ends thereof, and the gear 160 is fixed to one of the flanges 151. According to such an embodiment, the same effect as the previous embodiment can be obtained.

  Next, another embodiment of the present invention will be described. FIG. 26 is a view showing a part extracted from the center of the exposure head and the photosensitive drum of the image forming apparatus according to another embodiment, and is a view of the part from a direction orthogonal to the first direction. 26, reference numeral 152 denotes a photosensitive drum side coupling, 170 denotes a connection member, 171 denotes a second rotating shaft, 172 denotes a connection member side coupling, and 173 denotes a gear.

In the present embodiment, a photosensitive drum side coupling 152 is provided at one end of the photosensitive drum 150, and the connection member side coupling 172 of the connection member 170 is associated with the photosensitive drum side coupling 152. It comes to match. The connecting member 170 has a structure in which a gear 173 is arranged at one end of the second rotating shaft 171 and a connecting member side coupling 172 is arranged at the other end, and a rotational driving force from a driving device (not shown) is a gear. The signal is transmitted to the photosensitive drum 150 via 173. Even in the case where the photosensitive drum 150 is driven through such a connecting member 170, Da> (1/2) × G between the gear pitch G by the gear 173 and the width Da between the imaging optical system rows 106.
By configuring so that the above relationship is established, it is possible to obscure the influence of banding in the formed image.

  Next, an imaging optical system having a negative optical magnification will be described. In the present embodiment, a micro lens array (MLA) is used for the imaging optical system 104. This microlens array (MLA) is an imaging optical system having negative optical magnification. FIG. 27 is a view for explaining exposure by the imaging optical system having a negative optical magnification.

  In the exposure head 100 of FIG. 27, two groups of four light emitting elements 102 provided so as to be shifted in the first direction and the second direction form one light emitting element group. A single imaging lens 110 is provided corresponding to the light emitting element group. Here, as shown in the figure, when the light emitting elements are numbered 1 to 8, the odd numbered light emitting elements and the even numbered light emitting elements are arranged alternately.

  The imaging optical system having a negative optical magnification used in the present embodiment forms an inverted image as shown in the figure, and the surface of the photosensitive drum 150 is moved in the direction R in the drawing. In order to draw a linear latent image in the first direction, first, odd-numbered light emitting elements are caused to emit light at a certain timing to form odd-numbered imaging spots on the surface of the photosensitive drum 150. Then, after moving the surface of the photosensitive drum 150 by a predetermined amount, the even-numbered light emitting elements are then caused to emit light to form even-numbered imaging spots on the surface of the photosensitive drum 150.

  The line head, the image forming apparatus and the image forming method using the same according to the present invention have been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made.

It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is a flowchart which shows the process sequence of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is a block diagram which shows embodiment of this invention. It is a flowchart which shows the process sequence of this invention. It is explanatory drawing which shows embodiment of this invention. It is a block diagram which shows embodiment of this invention. It is a flowchart which shows the process sequence of this invention. It is explanatory drawing which shows the example which does not perform exposure position shift correction. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. 1 is a longitudinal side view of an image forming apparatus according to an embodiment of the present invention. It is explanatory drawing which shows a prior art example. It is explanatory drawing which shows a prior art example. It is explanatory drawing which shows a prior art example. It is explanatory drawing which shows other embodiment of this invention. It is explanatory drawing which shows other embodiment of this invention. It is explanatory drawing which shows other embodiment of this invention. It is a figure explaining the calculation method of a gear pitch. It is explanatory drawing which shows the effect by other embodiment of this invention. It is explanatory drawing which shows other embodiment of this invention. It is explanatory drawing which shows other embodiment of this invention. It is a figure explaining the exposure by the imaging optical system which has a negative optical magnification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Light emitting element, 3 ... Light emitting element, 4, 5 ... Imaging lens array, 4a, 5a, 14a ... Imaging lens, 6 ... Light emitting element group , 7... Light emitting element group row, 11... Photoconductor (latent image carrier), 20, 20 a... Control unit, 21... Print controller, 22. Head controller, 23a ... EEPROM communication control unit, 23b ... UART control unit,
24 ... Driver controller, 26 ... Video I / F, 27 ... Sub-scanning deviation correction unit, 28 ... Head control signal generation unit, 29 ... Request signal generation unit, 30 ... Registration Sensor, 35a to 35g ... LED chip, 37a to 37g ... Memory, 38 to 40 ... Light emitter array, 41 (Y, M, C, K) ... Photoconductor, 101 (Y, M , C, K) ... line head, P ... recording medium, Y, M, C, K ... image forming station, 100 ... exposure head, 101 ... light emitting element substrate, 102 ... Light emitting element 103 ... Light emitting element group 104 ... Imaging optical system 105 ... Light emitting element row 106 ... Imaging optical system row 110 ... Imaging lens 150 ...・ Photosensitive drum, 151... Flange, 152. Photoconductor drum side coupling, 155... Rotation shaft, 160... Gear, 170... Connection member, 171... Second rotation shaft, 172. ··gear

Claims (13)

A photosensitive drum having a rotation axis in a first direction;
A plurality of imaging optical systems that are arranged in the first direction and the second direction and have negative optical magnification, and a plurality that emit light that is imaged on the photosensitive drum by the one imaging optical system. An exposure head having a light emitting element substrate on which the light emitting element is disposed,
The image forming apparatus, wherein the light imaged by the imaging optical system arranged in the second direction forms an image at different positions of the photosensitive drum in the second direction.   2. The image forming apparatus according to claim 1, wherein the imaging optical system disposed in the second direction forms an image of light from the light emitting element at a position of the photosensitive drum different in the first direction.   The image forming apparatus according to claim 1, wherein the imaging optical system is arranged in a straight line in the first direction to form an imaging optical system row, and a plurality of the imaging optical system rows are provided. . Driving means for driving the photosensitive drum;
A gear having a pitch G for transmitting a driving force from the driving means to the photosensitive drum,
A width Da between the plurality of imaging optical system rows;
Da> (1/2) × G
The image forming apparatus according to claim 3, wherein:   The image forming apparatus according to claim 4, wherein the gear is disposed on a rotation shaft of a photosensitive drum.   The image forming apparatus according to claim 4, wherein the photosensitive drum has a flange, and the gear is fixed to the flange.   5. The image forming apparatus according to claim 4, wherein the image forming apparatus is connected to the driving unit and the photosensitive drum, and has a connection portion having a second rotation shaft, and the gear is disposed on the second rotation shaft. .   8. The control unit according to claim 4, further comprising a control unit configured to form a linear or substantially linear latent image in the first direction of the photosensitive drum by varying a light emission timing of the light emitting element in the imaging optical system row. 2. The image forming apparatus according to item 1.   The image forming apparatus according to claim 1, wherein the imaging optical system includes two or more lenses.   The image forming apparatus according to claim 1, wherein the light emitting element is an organic EL light emitting element. A first imaging optical system row in which a plurality of imaging optical systems having a negative optical magnification in the first direction are arranged;
A plurality of imaging optical systems having a negative optical magnification in the first direction and a second image forming an image at a position of the photosensitive drum different in the second direction from the first imaging optical system row An imaging optics line;
A plurality of light emitting elements for emitting light imaged by one of the imaging optical systems;
A photosensitive drum that moves in a second direction,
Emitting light imaged in the first imaging optical system row to form a latent image on the photosensitive drum;
A step of moving the photosensitive drum for a predetermined time after forming a latent image in the first imaging optical system row;
After moving the photosensitive drum for a predetermined time, emitting light imaged by the second imaging optical system row to form a latent image on the photosensitive drum;
An image forming method comprising: A first imaging optical system row in which a plurality of imaging optical systems having a negative optical magnification in the first direction are arranged;
A plurality of imaging optical systems having negative optical magnification in the first direction, and a second imaging optical system row that forms an image at a different position in the second direction from the first imaging optical system row When,
A plurality of light emitting elements for emitting light imaged by one of the imaging optical systems;
An exposure head comprising:   The exposure head according to claim 12, wherein a plurality of the plurality of light emitting elements that emit light imaged by the one imaging optical system are arranged in a first direction and a second direction.

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